From the Editor

People with mental disorders often have family members who have been touched by illness – a genetic tie, well established in the literature. But what about the influence of peer groups? A small body of literature suggests a connection between social circles and diagnosis. How can we understand this? Are mental disorders contagious?

In the first selection, Jussi Alho (of the University of Helsinki) and her co-authors attempt to answer those questions in a new study for JAMA Psychiatry. They did a cohort study, drawing on Finnish databases, and involving more than 700 000 people. They considered individuals who had a classmate diagnosed with a mental disorder in grade 9. “We found an association between having peers diagnosed with a mental disorder during adolescence and an increased risk of receiving a mental disorder diagnosis later in life.” We analyze the study and its implications.

How have cannabis poisonings increased with the legalization of edibles in Canada? In the second selection, a research letter for JAMA Internal Medicine, Dr. Nathan M. Stall (of the University of Toronto) and his co-authors looked at an 8-year period and focused on older adults, finding 2 322 ED visits in Ontario. “The largest increases occurred after edible cannabis became legally available for retail sale, a phenomenon similarly observed in Canadian children.”

And in the third selection, Caroline Payton Harmon, who is a PhD candidate at Rutgers University, describes the people she met in substance use treatment. The essay, published in The Lancet Psychiatry, is personal and notes the contrasts between those of different socioeconomic backgrounds. “The health-care system sees money and sees patients who are not worth the cost of treatment.”


Selection 1: “Transmission of Mental Disorders in Adolescent Peer Networks”

Jussi Alho, Mai Gutvilig, Ripsa Niemi, et al.

JAMA Psychiatry, 22 May 2024

Mental disorders are major contributors to the global disease burden, having detrimental individual, societal, and economic impacts. When investigating the impacts of mental disorders, the focus has typically been on the directly affected individual. It is, however, well established that the immediate family members are also adversely affected. Empirical findings suggest that harmful effects extend beyond the immediate family to friends and peers via social networks. For example, a longitudinal cohort study where a social network of 12 067 adults was followed up over 20 years indicated that depressive symptoms appear to transmit from person to person.

Investigating the transmission of mental disorders is especially important in childhood and adolescence. These are key developmental periods when the onset of many mental disorders is most likely to occur and when enduring peer networks and behaviors are established, particularly in the context of peer relationships.

So begins a study by Alho et al.

Here’s what they did:

  • They conducted a population-based registry study using Finnish databases (national health and school registries) to examine mental disorder diagnoses.
  • Individuals born between 1985 and 1997 were included. 
  • The cohort was followed from August 1 of the ninth grade (approximately age 16) until a diagnosis of mental disorder, emigration, death, or 31 December 2019.
  • They considered those who had exposure (“one or more individuals diagnosed with a mental disorder in the same school class in the ninth grade.”) versus those who didn’t.
  • The main outcome: Being diagnosed with a mental disorder during follow-up.

Here’s what they found:

  • There were 713 809 cohort members.
  • Demographics and diagnosis. Most were male (50.4%) with a median age at the start of follow-up of 16.1 years. 6.7% had a mental disorder diagnosis by the ninth grade
  • Follow up. “25.1% were diagnosed with a mental disorder, corresponding to an incidence rate of 2 283 per 100 000 person-years at risk.” 
  • Classmate connection. “Having more than 1 diagnosed classmate with any of the examined mental disorders was associated with a 5% higher risk of later diagnosis (HR, 1.05…).” (!)
  • Time. “During the first year of follow-up, the risk of being diagnosed was 9% higher with 1 diagnosed classmate (HR, 1.09…) and 18% higher with more than 1 diagnosed classmate (HR, 1.18…). After the first year of follow-up, the risk of being diagnosed was statistically significant during years 4 and 5 with 1 diagnosed classmate with a mental disorder and in all 3 time windows with more than 1 diagnosed classmate with a mental disorder.”
  • Mental disorders. The risk was highest for mood, anxiety, and eating disorders.

A few thoughts:

1. This is an excellent paper with a big dataset and published in a major journal. As the authors write: “To our knowledge, the present study is the largest and most comprehensive investigation on this topic to date.”

2. The main finding in a sentence: “This study suggests that mental disorders might be socially transmitted within adolescent peer networks.” Of course, it was dose dependent: one peer didn’t make a difference but two or more did.

3. How to explain this? The authors write: “One plausible mechanism is the normalization of mental disorders through increased awareness and receptivity to diagnosis and treatment when having individuals with diagnosis in the same peer network. Similarly, having individuals with no diagnosis in the peer network might discourage seeking help for any underlying mental health problems.” This explanation seems credible – illness in peers may encourage people to get help (and a less bold explanation than mental disorders spreading like viruses).

4. Like all studies, there are limitations, and the authors note several. They write that, with small HRs, “we cannot rule out residual confounding due to unmeasured or inaccurately measured covariates in this cohort study.” (!!)

The full JAMA Psych paper can be found here:

Selection 2: “Edible Cannabis Legalization and Cannabis Poisonings in Older Adults”

Nathan M. Stall, Shengli Shi, Kamil Malikov, et al.

JAMA Internal Medicine, 20 May 2024

In October 2018, Canada legalized the sale of dried cannabis flowers for nonmedical use, and in January 2020, edible cannabis became legally available for retail. In California, legalization of all forms of nonmedical cannabis has been associated with increased cannabis-related emergencies in older adults (aged ≥65 years). Limited information exists on the specific health outcomes of nonmedical edible cannabis use in older adults; thus, we examined the association between edible cannabis legalization and emergency department (ED) visits for cannabis poisoning in older adults residing in Ontario, Canada.

So begins a research letter by Stall et al.

Here’s what they did:

  • They conducted a retrospective, population-based, cross-sectional study examining ED visit rates for cannabis poisoning in older adults.
  • They drew on Ontario Ministry of Health administrative data and looked at three policy periods: “prelegalization (January 2015 to September 2018); legalization period 1, which permitted the sale of dried cannabis flowers only (October 2018 to December 2019); and legalization period 2, which also permitted the sale of edible cannabis (January 2020 to December 2022).”
  • They identified ED visits where cannabis poisoning was the main or contributing reason and calculated rates (per 100 000 older adults). They also did a Poisson regression model to calculate incidence rate ratios (IRRs).

Here’s what they found:

  • During the 8-year study period, there were 2 322 ED visits for cannabis poisoning in older adults.
  • Demographics. The majority were men (55.2%) with a median age of 69.5 years.
  • Comorbidities. Among patients with cannabis poisoning, 16.6% had concomitant alcohol intoxication, 38.5% cancer, and 6.5% dementia.
  • Across time. “During legalization period 1, the rate of ED visits was substantially higher than prelegalization (15.4 vs 5.8 per 100 000 person-years; adjusted IRR, 2.00…). During legalization period 2, the rate of ED visits (21.1 per 100 000 person-years) was significantly greater than prelegalization (adjusted IRR, 3.08…).” See figure below.

A few thoughts:

1. This is an interesting and relevant research letter.

2. The main finding: “Cannabis legalization in Canada was associated with increased rates of ED visits for cannabis poisoning in older adults.”

3. We tend to focus on cannabis and youth. This research letter is a reminder that all age demographics can be affected by legalization.

4. How to explain the rise of poisonings? In an accompanying editorial, Drs. Lona Mody (of the University of Michigan) and Sharon K. Inouye (of Harvard University) consider some reasons.

“It is important to recognize that current cannabis is much more potent than in the past. With edible cannabis products, it is difficult to know what is being ingested by patients because active ingredients and doses are not specified. Increases in oral cannabis use are likely occurring for many reasons. Besides recreational or unintended use, it is possible that older adults use cannabis to self-treat conditions such as pain, nausea, and insomnia that might not be adequately treated by traditional routes.” 

They also remind us: “When surveyed, nearly half of older adults state that they do not discuss their nonmedical cannabis use with their clinicians.” Care for older adults should include consideration of substance including, yes, cannabis edibles.

5. Like all studies, there are limitations, including that they focused on ED data (a patient may have sought care elsewhere).

The full JAMA Int Med research letter can be found here:

Selection 3: “Health care discriminates, addiction does not”
Caroline Payton Harmon

The Lancet Psychiatry, March 2024

We are sitting in a circle at a substance use treatment facility, sun filtering through the trees into our group therapy room. She gestures to one of her legs. ‘It used to be way more swollen than this, like a balloon’, she tells us. ‘They say I got DVT, that’s like a blood clot or somethin’.’ My eyes widen, despite my best efforts to keep a neutral expression. Deep vein thrombosis – that can be deadly. She keeps going: ‘It’s happened like three or four times and I gotta keep goin’ back to the hospital for all my abscesses too.’ Her legs are pockmarked with scars, and her left calf is bulging against the laces of her hi-top sneakers…

My head swivels to look at Rachel, the therapist, who [says] ‘I don’t see your name on the check-in sheet, can you tell me what your mood is on a scale of one to ten and if you used heroin since the last time you were here?’ I turn back to Hazel. ‘I dunno, like a four?’ Hazel avoids Rachel’s second question. Rachel [the therapist] repeats the question. ‘On Friday’, Hazel says, flatly. Without changing her soft tone, Rachel questions: ‘And how much did you use?’ I can still hear Hazel’s response, see her in my mind, feel the anxiety rising up through me. ‘Two bags.’

So begins an essay by Harmon.

She goes into detail on Hazel’s struggles with substance – and her insurance. “While we are on break, Hazel tells me that she is angry with Rachel. When I ask why, she informs me that she might get kicked out of the program because she used. Her health insurance will only cover abstinence-based treatment and she is required to stay sober while in the program. I didn’t know they could do that. It isn’t fair. I relapsed in the first couple of weeks while in this program, but I am still here. Why do I get to stay but Hazel does not?  I do not see Hazel again after that day.” She wonders what happened to her. “She could be dead now.”

She also notes the difficulties of another patient, Heaven, who is “homeless and staying in emergency housing right now.” She describes her predicament: “She could go back to her mom’s house, but her mom’s boyfriend molested her and her brother gets violent during his own mental health episodes.” While the therapist is doing everything she can to prove that Heaven is in treatment and needs housing, Heaven ultimately has to vacate emergency housing. “I do not see Heaven again after Labor Day. I do not know where she is now.” 

“Addiction is ferocious. It finds the vulnerable gaps in your armor and sinks its teeth into the soft flesh underneath. The venom of addiction quickly begins to poison and dissolve your flesh, empty you of your will, and destroy the person you were. Everyone in my treatment group has a story like this. Heaven comes from an abusive home, where she never felt safe. Drugs made her feel invincible at first. That is, until her daughter was taken away from her. Hazel tells us she was a normal teen, but she was insecure and alcohol gave her confidence. Now, at age 30, she describes homelessness in the Kensington neighborhood of Philadelphia, the city with the highest rate of drug overdose in the USA.”

She notes that addiction doesn’t discriminate. “A tech entrepreneur joins our group towards the end of my time in the program. He made millions on various start-up companies, but when bipolar disorder sent him into severe manic and depressive episodes, the soothing whispers of addiction offered him a cure. Now his marriage is over. His children do not want to see him… One woman drives a luxury car to the outpatient facility every day. An expensive purse is always draped over one arm. She tells us about her second house at the beach.”

“Although addiction does not discriminate, the health-care system certainly does.” The author notes the contrast: “Hazel can only afford the most basic health insurance, which then refused to cover her treatment at the first opportunity” while the “tech entrepreneur does not worry about health insurance.” 

She notes her own situation. “I have had the privilege of growing up with supportive, financially stable parents. I am a White woman. I am dealing with disabling mental illness and addiction, just like Hazel… But I am significantly more likely to have long-lasting, successful recovery simply because of the privilege I was born into.”

She closes by telling her story. “I am sober now and enrolled as a PhD candidate in a Nutritional Sciences Program, studying a topic for which I have a deep passion. I engage in activities every day to maintain my sobriety, to build my life back, and to be a positive presence for others. And I also think of Heaven and Hazel every day.”

A few thoughts:

1. This is a good and moving essay.

2. The contrast is striking and well described.

3. I’ll make a comment that I’ve made before: it’s amazing and important that people like that author are willing to come forward and tell their story.

The full Lancet Psych article can be found here:

Reading of the Week. Every week I pick articles and papers from the world of Psychiatry.