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Home – Child Mental Health Blog

Toxoplasma Gondii Infection Linked to Aggression and Intermittent Explosive Disorder

Posted: March 31st, 2016 by David Rettew

A new study creating lots of both media attention and puzzled looks explores the link between psychiatric disorders, particularly those that involve aggression and irritability, and latent infection with the protozoan parasite toxoplasma ghondii (T gondii).  In hearing about this study, the first reaction of many might be why anyone bothered to look at this link in the first place.  Cats are known hosts of the parasite, but infection can occur in humans from infected cat feces in addition to eating

photo by BK images and freedigitalvideos.net

photo by BK images and freedigitalvideos.net

undercooked meat or drinking contaminated water.  Human infection is common but usually not dangerous, unless someone is immunosupressed.   While not an agent with a huge literature behind it in terms of behavioral health, there have been previous associations found between latent toxoplasmosis infection and psychiatric symptoms, including a larger study in 2015.  There also exists a literature on the behavioral effects of T gondii in animals.  Thus, this study did not just come totally out of the blue.

For this investigation, the authors assessed three groups of adults (total n=358), including healthy controls, a group with well diagnosed intermittent explosive disorder (IED: characterized by episodes of severe impulsive aggression), and another group who met criteria for DSM-5 psychiatric disorders other than IED.  Aggression and impulsivity were assessed with various known rating scales, and toxoplasmosis status was assessed using a blood test for IGG antibodies.    

The overall rate of T. Gondii seropositive subjects was 15.9% which evidently (and a little unsettlingly to be honest) is close to national norms.  Statistically higher overall scores on aggression and impulsivity scores were found among subjects who were seropositive for T. Gondii, while, contrary to some previous work, no differences were found related to suicide or self-directed aggression.  In terms of the three diagnostic groups, the percentage of subjects with IED who were seropositive for T. Gondii was 21.8%, which was significantly higher than controls (9.1%) but not psychiatric controls (16.7%).

The authors concluded that their data support others that suggest a link between T. Gondii and aggression.  (Actually, in the abstract they say it supports the link with self-directed aggression but I think that is a mistake).

In the discussion section, the authors go into some speculation about why this link might exist, including possible low grade chronic inflammation in the brain, alterations of corticolimbic circuits, or even via increased production of testosterone, based on some animal studies.  Other than once mentioning that T Gondii infections are treatable, the article gives no advice about assessing or treating the infection in aggressive people, likely because their cross sectional data require further investigation using other designs.  I haven’t heard any official response from the cat lobby.


Coccaro EF, et al.  Toxoplasma gondii infection:  Relationship with aggression in psychiatric patients.  J Clin Psychiatry 2016; 77:334-341



Mental Health of Transgender Children Who Have Socially Transitioned

Posted: March 15th, 2016 by David Rettew

While it has been shown in many studies that transgender youth frequently struggle with significant emotional-behavioral problems, the million dollar question behind this association is the degree to which these symptoms are driven by the intense stigma, lack of acceptance, and

Photo from imagerymajestic and freedigitalphotos.net

Photo from imagerymajestic and freedigitalphotos.net

even outright maltreatment that many of these children and adolescents suffer.  This question is relevant not only to point the way for optimal intervention but also for the controversy surrounding the continued inclusion of gender dysphoria, previously known as gender identity disorder, in the DSM5.

To examine this issue further, a group of researchers from the TransYouth Project followed a sample of 73 prepubescent transgender children between the ages of 3 and 12 who had socially transitioned at both home and school.  This group was compared cross-sectionally to a sample of nontransgender children as well as a subset of siblings of the trangender children.  The main outcome variables were levels of anxiety and depression as measured by the seldom used parent-report questionnaires, the National Institutes of Health Patient Reported Outcomes Measurement Information System. Of note, the transgender children included in this study needed to believe, and not simply wish, that they were actually of the “opposite” gender.   Also, none of the subjects, 70% of whom were natal boys who now identified as female, had received any hormonal treatment at the time.

Relative to the control groups or to national norms for the rating scales, the transgender children showed no elevations on depression scores. Some statistically significant differences were found, however, with the transgender group with regard to anxiety, although the mean score for the transgender group (at 54) was not in the clinical (above 63) or even preclinical range (above 60).   This finding did not vary according to natal sex.

The authors concluded that their data support the idea that psychiatric symptoms are not inherent in transgender children and that supporting parents and schools in their social transition can result in improved mental health.

While informative, the study does have some limitations.  First, one definitely gets that the sense the TransYouth Project was hoping to find the results they did to better advocate for transgender children.  While it is probably true that most researchers hope to find a specific result in their studies, this fact probably does have an impact in how the study is interpreted (for example, highlighting the lack of depression rather than the increased anxiety they found).  The results also would have been a bit more compelling if the researchers used more widely known rating scales and gathered information from sources other than parents, who might be motivated to demonstrate that their efforts were successful.  It would also have been very helpful to present the percentage of children in each group in the clinical and preclinical range for depression and anxiety rather than just the group means.

These problems aside, this study provides some important data, suggesting that transgender children who are provided support and acceptance in their social transition can often be spared much of the anguish that unfortunately befalls many others.


Olson KR, et al. Mental Health of Transgender Children Who Are Supported in Their Identities.  Pediatrics 2016, epub ahead of print.


Prevention Efforts at Suicide Hotspots

Posted: February 17th, 2016 by David Rettew

As reported recently in the Vermont Digger, there is a bill (H. 593) in the Vermont Legislature that would require some sort of suicide prevention action to be taken at the Quechee George Bridge, where there have been 8 suicides since 2008 (more than all other Vermont bridges combined).

While there are few people opposed to preventing suicide, there remain some legitimate questions about the bill and the effectiveness of similar efforts at other suicide “hotspots” such as the Golden Gate Bridge in San Francisco or several bridges around Cornell University in Ithaca, New York.  People wonder about how effective such measures really are since people who are suicidal could simply go somewhere else.  There are also concerns over spoiling the access or view of many people who gain benefit from being in these often beautiful places.Quechee Bridge

What is actually known about the value of trying to deter suicides at these particular places?  A  recent article in Lancet Psychiatry used meta-analytic techniques to provide a more definitive answer.   The authors searched for scientific studies that assessed the effectiveness of hotspot suicide prevention.   They point out that, while most people think of prevention efforts mainly in terms of restricting access through fences or nets, other types of interventions also can be implemented.  Among these are efforts to encourage help-seeking (e.g. placing help lines phones at the site) and increasing the possibility of intervention by a third party (e.g. having more personnel near the site).  In examining whether or not suicide prevention works, the authors divided the studies they found based on the type of intervention that was used (although some places had more than one).   The primary outcome variable was a pooled incidence rate ratio (IRR) that reflected the change in number of suicides after the intervention was introduced.  The length of time suicides were assessed prior and after the intervention ranged widely from 5 months to 22 years.

A total of 18 studies were identified, most of them related to efforts designed to prevent suicides at bridges and cliffs.  By far the most common type of intervention were those that did restrict access.  Overall, suicide rates dropped from 5.8 suicides per year to 2.4.   In terms of intervention type, restricting access and increasing the possibility of third party involvement were significantly related to suicide reduction.  For measures that encouraged help-seeking, there was also support for this intervention but this positive result required the removal of one outlier study.

The authors concluded that interventions at suicide hotspots are effective.  Furthermore, they state that their finding of effectiveness for interventions other than restricting access supports the notion that these improvements are not simply the result of individuals substituting one place for another.


Pirkis J, et al.  Interventions to reduce suicides at suicide hotspots: a systematic review and meta-analysis.  Lancet Psychiatry 2015 Nov;2(11):994-1001


Higher Guanfacine Doses Found Effective for Adolescent ADHD

Posted: February 4th, 2016 by David Rettew

While stimulants generally remain first-line medication for ADHD, alternatives are often needed due to side effects or ineffectiveness.   Of the non-stimulant medications, guanfacine and its more recent extended release preparation (trade name Intuniv) is one possible alternative.  Current FDA guidelines specify 4mg per day as the maximum dose, although much of this recommendation is based on younger children.  There is some data suggesting that guanfacine may be less effective in adolescents, and this recent industry sponsored study set out to see if perhaps one reason was due to insufficient dose.  Here the authors conduct a multi-center, double-blind placebo-controlled randomized trial  of extended release guanfacine attempting to achieve a dose of between 0.05 and 0.12 mg/kg/day, which is about the typical dose in younger children on a per weight basis.

The subjects were 314 adolescents between the ages of 13 and 17 with a confirmed ADHD diagnosis.  Psychiatric comorbidity other than oppositional defiant disorder (ODD) was Guanfacineexclusionary.  Most of the sample had previously tried a stimulant.  Subjects at risk for cardiovascular problems or who were taking medications that “have central nervous system effects” were excluded from the study.  Extended release guanfacine was initially dosed at 1mg per day and titrated according to response and tolerability to a maximum of 4mg per day for patients weighing less than 41kg and up to 7mg per day for patients weighing more than 58kg.  The medication was given once per day in the morning.  The primary outcome measure was changes in scores on the ADHD Rating Scale IV, the Clinical Global Impressions scale and the Weiss Functional Impairment Rating Scale.  Side effects and vital signs were also monitored during this 13-week study.

In terms of results, a total of 85% of the sample was able to achieve their optimal dose with nearly half the sample taking 5-7 mg per day.  At the end of the study (using a last on-treatment assessment carry forward analysis), 66.9% of the guanfacine, compared to 45.8% of the placebo group were classified as responders, based on at least a 30% improvment in the ADHD Rating Scale.  Improvement in ADHD symptoms with guanfacine was found to be statistically superior to placebo starting on week 7, although no significant group differences were found on any domains of the functional impairment scale.  In terms of side effects, somnolence was reported in 44% of the guanfacine group with headache occurring in 27%.  As might be expected, small but significant differences were found for heart rate and blood pressure changes compared to placebo. Nine subjects discontinued the medication because of side effects.

The authors concluded that extended release guanfacine at doses up to 7mg per day is more effective than placebo in treating ADHD and was generally well tolerated.

One thing that was a bit unusual for this study  was the high placebo response rate.  Conventional wisdom states that placebo response rates tend to be low in ADHD studies and generally this is true: however, there have been other studies with high placebo response rates particularly with adolescents.

In my own practice, guanfacine is also a medication I consider for youth who can be dysregulated and aggressive, particularly those whose aggression tends to be more reactive.  In some cases I’ve been able to avoid what to me are riskier medications such as antipsychotics.  This study suggests that if patients are tolerating this medication well, it may be worth considering pushing the dose further before giving up on the medication.

I should state that I don’t personally don’t receive any money from the manufacturers of extended release guanfacine.  This study, however, was sponsored by a pharmaceutical company, and I know these days that tends to raise some skepticism about the results.  The lead author is a well respected child psychiatrist who is currently the Director of Child Psychiatry at Massachusetts General Hospital.


Wilens T.  A Randomized, Placebo-Controlled Trial of Guanfacine Extended Release in Adolescents With Attention-Deficit/Hyperactivity Disorder.  JAACAP 2015;54(11):916–925.

Six Vermont Physician Organizations Endorse Statement Detailing Risks of Legal Cannabis

Posted: January 28th, 2016 by David Rettew

On Thursday January 28, representatives from six Vermont medical organizations (VT chapters of the American Academy of Pediatrics, American Association of Child & Adolescent Psychiatry, Family Medicine, and American College of Physicians as well as the Vermont Psychiatric Association and the Vermont Medical Society) held a press conference at the Statehouse in Montpelier to outline concerns about the proposed legalization of marijuana.

All six groups endorsed a single document that can be found below which outlines known health risks associated with cannabis use, particularly with youth.  The group expressed concern that legalization would likely only add to the current drug problem in the state and cautioned against making a permanent decision for Vermonters without knowing the true costs of legalization, as data from states like Colorado and Washington only slowly becomes available (with much of it so far not good news).

The press conference was attended by several media groups as well as by representatives of the legislature.  The Judiciary committee is expected to approve the bill out of committee on Friday January 29 to be considered by the full Senate and House.

Press Release – Legalization of Cannabis

Debunking the ‘Sticks and Stones’ Myth – Emotional Abuse May Hurt Just As Much

Posted: January 27th, 2016 by David Rettew

(Editor’s note:  I am very pleased to present this post written by one of our child psychiatry fellows – DCR)

by Sara Pawlowski, MD

It is indisputable that child abuse is devastating for children with widespread effects on a child’s physical and mental health. It is also widely believed that certain forms of child maltreatment, namely physical and sexual abuse (with reported prevalence rates of 8% and 1.6 % respectively) have more negative effects on children than emotional or verbal abuse. In this way, there exists a sort of hierarchy of abuse types where physical and sexual abuse represent the most severe form of child abuse punishable by law. Meanwhile, emotional and verbal

photo by David Dominici and freedigitalphotos.net

photo by David Dominici and freedigitalphotos.net

abuse (which includes behaviors such as ridicule, intimidation, rejection, and humiliation with a much higher prevalence rate of up to 36.3%) represent a possibly less impactful form of abuse which often fails to have any clear actionable clinical or legal guidelines. There are also stereotypes that exist about children who are abused and how they may develop and behave as a consequence of this maltreatment. Generally, it is thought that emotional abuse creates a depressed, anxious and withdrawn child while physical abuse leads to aggression and bullying others.

A recent study, however, tested the hypothesis that all forms of abuse have deleterious consequences and that these categorizations of abuse types and victim profiles are oversimplified. Using data obtained from a research summer camp which has existed for over 20 years to study a diverse set of low-income children from ages 5-13, they analyzed child protective services’ reports, children’s self-reports on depression, peer ratings of aggression, interviews with mothers and observations of the children at camp by staff members. In a total group of about 2,300 children who attended the camp over the years, about half of them had been maltreated. From these data, they separated out two groups into a non-maltreated and maltreated group with subcategories according to types of abuse and several other relevant measures. Then, they looked for corresponding mental health outcomes in children such as depressed mood and aggressive behaviors. The researchers asked: did these children have any pattern of response to abuse consistent with our broad cultural assumptions? Were the physically abused children more physically abusive to peers? Were the emotionally abused children more withdrawn and depressed? And, ultimately, did the type of abuse correspond to any discernable pattern of mental health outcome that we could predict?

What they found was striking in that the severity, frequency, diversity (meaning that that a child endures multiple, diverse forms of abuse) and duration of any type of abuse regardless of type (physical, sexual, emotional or neglect) led to global negative effects on mental health. Additionally, the type of abuse was not predictive of a child’s mental health outcome. In short, physical abuse is just as likely to lead to a child’s depression as emotional or verbal abuse. This study emphasizes that severity, frequency and duration of abuse predicts poor mental health outcomes rather than the specific type of abuse.

It is still within many clinicians’ repertoire of questions to ask when someone feels threatened or intimidated if there has also been physical abuse or action on these threats. While this may still be an important question to ask, this study suggests that the threats alone may have a negative impact on the child. If the impact of the most prevalent type of abuse, emotional and verbal abuse, is potentially as dire as other forms of abuse, it may be important to shift our interactions with children and families to reflect this understanding and emphasize prevention of all forms of abuse. And given the likelihood that emotional and verbal abuse will continue to be less actionable by child protection agencies, the task of reducing and preventing it may fall to us as clinicians.

In the future, the research team hopes to continue his work to examine how abuse impacts not just a child’s expression of mental health symptoms but also of a child’s personality and temperament. He wonders if child abuse can also change who a child is, their personality, how they think, feel, act and the very fabric of their identity. These are troubling suggestions but they also represent a more nuanced, complex understanding of the gravity of the impact of child abuse on a child’s development. Hopefully, the realizations as outlined in this study will result in prevention efforts for all kinds of maltreatment with the acceptance of the universal negative impact that abuse has on children.

Reference: Vachon, David D., Robert F. Krueger, Fred A. Rogosch, and Dante Cicchetti. “Assessment of the Harmful Psychiatric and Behavioral Effects of Different Forms of Child Maltreatment.” JAMA Psychiatry 72.11 (2015): 1135.

Very High Rates of Psychotic Symptoms Linked to Stimulant Medications

Posted: December 28th, 2015 by David Rettew

(Note: portions of this review were recently published in an article in Clinical Psychiatry News)

While it is known that stimulant medications used to treat ADHD might occasionally to lead to psychotic symptoms, this side effect is considered to be rare and usually associated with either medication abuse or very high dosages.  A report just released today in the journal Pediatrics, however, now calls into question how rare psychotic symptoms from stimulants might actually be.

The data for this study come from the Families Overcoming  Risks and Building Opportunities for Wellbeing study.  The sample size was small but thoroughly evaluated. A total of  141 children in Ritalinwhich at least one of the parents was diagnosed with a major mental illness, mainly major depressive disorder and bipolar disorder but also schizophrenia (5%).  The mean age of the children was about 12 years old.  Of these children, 24 (or 17%) had taken stimulant medication.  Psychotic symptoms or psychotic like experiences were assessed through four different methods including an instrument called the “Funny Feelings” interview with psychotic symptoms counted as present any of their four ascertainment methods yielded a positive result.  The main analysis was a logistic regression examining the association between lifetime use of stimulant and lifetime use of a psychotic or psychotic like experience.   The analyses controlled for age, gender, and family history.

The major finding of the study was that psychotic symptoms were quite common, present in one-third of this sample overall, and were found to be more likely among those children taking stimulants.  A total of 62.5% of children taking stimulants versus 27.4% of children who had not, reported some kind of psychotic symptoms.  After account for some potential confounding variables, the odds ratio related to taking stimulants was 4.41 which was found to be statistically significant.  The odds ratio related to ADHD itself and psychosis was 1.98 but this was not significant due to the small sample size.  When looking at current stimulant use, the rate of current psychotic symptoms was 27%. The type of psychotic symptoms ranged widely and included a number of children with auditory and visual hallucinations.

The authors concluded that psychotic symptoms may be more likely to occur among children with a family history of mental illness, particularly when taking stimulant medications.  They urge close monitoring of these symptoms during treatment.

It is likely that many practicing clinicians are going to be quite stunned to see rates of psychotic symptoms this high.  While the study will surely activate the current anti-medication fervor common among those who don’t see patients, many practicing physicians will likely find that these rates simply don’t fit with clinical experience.  Indeed, there may be some reason to be cautious in interpreting these results.  As mentioned, the sample size was quite small, and psychotic symptoms were almost exhaustively assessed.  Yet strangely, association between psychosis and stimulant dose were not examined.  Perhaps most limiting, overall level of psychiatric symptoms in children was not controlled for in the analysis. As a result, it is hard to know whether the group taking stimulants was more impaired from the start.

Nevertheless, this study suggests that more vigilance and perhaps more rigor is needed when querying for possible psychotic symptoms among children who take stimulant medications, particularly among youth who have a family history of major mental illness.

Ironically, while the intent of the study certainly is to advise caution in the use of psychiatric medications, the article could lead to the opposite, if more antipsychotic medications are used to treat these more subtle symptoms.  This would be unfortunate, in my view, until these results are more thoroughly replicated using a randomized design.  Studies like this remind us to maximize many non-pharmacological treatments that can be effective in ADHD.


MacKenzie LE, et al.  Stimulant Medication and Psychotic Symptoms in Offspring of Parents With Mental Illness.  Pediatrics 2015; epub ahead of print.

Melatonin: What Do We Really Know?

Posted: December 11th, 2015 by David Rettew

It is probably safe to say that melatonin has become the go-to agent for the treatment of children who struggle to fall asleep. According to a recent article in the Wall Street Journal, melatonin is now a 260 million dollar market in this country where it is sold over the counter, unlike some European countries where a prescription is still required.

Melatonin is a hormone that is synthesized from the amino acid tryptophan in the pineal gland. Its release is controlled by the suprachiasmic nucleus of the hypothalamus with the level peaking in the evening.  The fact that our body makes melatonin naturally has  been one factor related to many primary care physicians and psychiatrists alike giving the hormone a “pass” when it comes to

Image by phanlop88 and freedigitalphotos.net

Image by phanlop88 and freedigitalphotos.net

scrutiny, but questions about both is efficacy and safety remain.

Recently, a selective review (which reads more like a commentary) about melatonin use in youth was published in the Journal of Paediatrics and Child Health.  While the article certainly seems to be trying to persuade as much as inform, the author makes some important and surprising points.  One is that animal studies have shown a range of effects on the reproductive system for melatonin that have not been well understood. Indeed, there still exists a registered use for melatonin in animals to increase fertility.  These effects on reproduction or puberty in humans have yet to be demonstrated, although the few studies that have examined this issue have been small and contain significant limitations.  It is also worth noting that melatonin is metabolized in the liver by the enzymes CYP1A2 and CYP2C19 which can be inhibited by antidepressants such as fluvoxamine and citalopram, respectively.  As melatonin is often used in conjunction with psychiatric medications, these potential interactions need to be considered.

With regard to efficacy, studies seem to support its usefulness, although perhaps not to the extent one might expect.  Two recent controlled trials in children found that melatonin increased sleep onset by about 30 to 45 minutes but it does not generally increase total amount of sleep.

The author concluded that the research on melatonin in children is inadequate, especially given the effects on the reproductive system documented in animal studies. He urged much more research before governing bodies decree melatonin as safe and effective.

The review was later criticized in a letter to the editor for omitting studies from melatonin prescription products such as Circadin which is approved in Europe (although not for kids).  In the USA, there is also the melatonin receptor agonist remelton (Rozerum) which also has some data but, again, is not approved for pediatric ages.

Counter-balancing the concern of melatonin is the large body of literature that demonstrates the negative effects of poor and inadequate sleep.   In trying to balance these concerns, I’m not sure I’m ready to take melatonin out of my bag (particularly in comparison to other sleep medications that are used).  At the same time, however, it is important not to use melatonin or any other sleep-aid as a shortcut to addressing behavioral measures.   Many children benefit from consistent routines that gradually wind down stimulation and prepare a child to settle down for the night, and families that try to circumvent this process often run into problems.  Exercise (or lack thereof) can also be a major player in why some kids just don’t feel tired at night.  Nevertheless, it is also certainly true that many children will struggle with sleep no matter how good the bedtime routine is.


Kennaway D.  Potential safety issues in the use of the hormone melatonin in paediatrics.  J Paediatrics Child Health.  2015: 51(6):584-589.



Primary Care – Got Child Psychiatry Consult?

Posted: December 9th, 2015 by David Rettew

The Vermont Center for Children, Youth and Families at FAHC/UVM, in partnership with VCHIP, is entering our fourth year of the Child Psychiatric Phone and Email Consultation Program. The goal of this program is to provide healthcare providers with free curbside phone and email consultation to assist in the management of emotional and behavioral problems in primary care settings. Examples of these consultations include assisting in assessment, diagnosis, medication management and Family Wellness recommendations.

Results taken from a questionnaire given before and after PCP’s have accessed our consultation service show that users confirm an increased ability to quickly access expert psychiatric consultation as well as experience an increase in confidence in diagnosing and treating children’s mental health issues.

Whether you are already familiar with our consultation services, or hearing about them for the first time, please review the below commitment.

We will:

  • Designate a child psychiatric specialist (MD or NP) to return your phone call/e-mail within 24 hours during the regular work week (weekend coverage is already available through the on call system).
  • Provide you and your staff with phone and E-mail access to our experienced Family Wellness Coach, Eliza Pillard, LICSW, who can help guide your practice in the search for evidence based interventions for emotional and behavioral problems on behalf of your patients.
  • Connect you to our VCCYF Primary Care blog http://blog.uvm.edu/drettew/ and VFBA (Vermont Family Based Approach) blog http://blog.uvm.edu/vfba/ which deliver regular postings on topics that may be relevant for your patients, such as updates on child mental health and family wellness research and interventions.
  • Update all participants with news of access to our services (e.g., our Autism Assessment Clinic), educational opportunities, and advances in our field.

Please note that this program will not serve as a rapid conduit for assessment and consultation at the VCCYF. As you know, we have a long waiting list and feel obligated to serve families on a first-come-first-serve basis.

If you are interested in accessing a consult, please contact Eliza at eliza.pillard@uvmhealth.org or (802) 847-9759. We look forward to hearing from you.



Jim Hudziak, MD, Director                                                                                                      Eliza Pillard, LICSW

Vermont Center for Children, Youth, and Families                                                            Family Wellness Coach

Study Explores Humans’ “Natural” Sleep Patterns

Posted: December 3rd, 2015 by David Rettew

Despite the fact the we spend nearly a third of our life asleep, many fundamental questions, such as how much sleep we really need, remain debated.   One popular view is that most of us living in modern cultures are chronically sleep deprived and this may be one of the causes of many health problems, from obesity to depression.

To try and get a better handle on natural sleep habits, some researchers recently published a study that examined the sleep patterns of three pre-industrial societies in Tanzania, Bolivia, and SleepNamibia that were mainly hunter-gatherer or hunter-horticulturalist groups. None of the three groups used modern conveniences to alter light or temperature.  Of chief interest were the basic statistics regarding sleep onset and duration and their relations to environmental variables such as light and temperature. Sleep was measured using watch like devices worn on the wrists for 6 to 28 days.

Interestingly (and fortunately for the researchers trying to synthesize their data), there were many similarities between the three societies with regards to sleep habits. The total sleep duration was found to range between 5.7 to 7.1 hours per day, with about 1 hour more of sleep occurring during the winter.   Initiation of sleep tended to occur about 3 hours after sunset with awakening occurring generally before sunrise.  Somewhat unexpected was that these patterns seemed to be as much related to temperature as light, with sleep onset occurring during the period of rapid temperature decline and awakening occurring around the time temperature is at its lowest.

Contrary to some data suggesting that our ancestors slept in two waves with a period of quiet wakefulness in between, extended periods of nocturnal awakening were rare. Napping was also not particularly common but did occur in about 7% of days during the winter and 22% of days in the summer (this was an estimate and may have counted periods of rest without sleeping). Interviews with subjects revealed that, despite none of the three cultures having a word for insomnia, the problem was reported by some, albeit at levels typically lower than that of industrialized societies.

The authors concluded that their data suggest, contrary to some popular opinions, that sleep in industrial societies has not been artificially reduced below natural levels due to the pressures of modern culture.  At the same time, however, there was evidence that modern sleep schedules have veered in some different ways, possibly due to all the artificial light and temperature controls we now enjoy.  

While definitely an interesting study, the clinical takeaway is not immediately clear.  One possible implication might be to relax our pushing of people to get at least 8 hours of sleep per night.  There could also be benefit for people with sleep problems to try and shift their schedules somewhat or create light and temperature variations that more closely mirror the natural world.


Yetish G, et al.  Natural Sleep and Its Seasonal Variations in Three Pre-industrial Societies.  Current Biology 2015; 25:1-7.


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