Life On Mars #5

Diagnostic inflation, increasing cannabis risks, and the promise of salmon and walnuts

This fortnight’s Life On Mars looks at spikes in diagnoses of some mental health and neurodevelopmental conditions, and what these mean; the mental health risks to teenagers of ever-stronger cannabis; and the potential of omega-3 fatty acids when it comes to mental health.

It comes during a week in which I’ve received my author copies of Teenagers: The Evidence Base (out on 30 January), with some early reviews here:

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Diagnoses of autism spectrum disorder and some mental health conditions have shot up

Study title: Association Between Autism Diagnosis Rates and Adolescent Depression: A Population-Based Study in Sweden (February 2025)

This study looks at ballooning diagnoses of autism spectrum disorder (ASD) and the potential that these diagnoses have to cloak other issues, such as depression, that affected teenagers may be experiencing.

The authors point out that some of the increase in ASD diagnoses may result from doctors applying less stringent diagnostic criteria than they did in the past. In other words, teenagers and younger children who wouldn’t have been given a diagnosis, say, twenty years ago might find themselves ticking the relevant boxes today. They also suggest that when healthcare professionals focus on ASD as a potential diagnosis, they can fail to spot mental health issues that may coexist with (or even explain) symptoms of ASD in some teenagers.

To test links between ASD and diagnosis rates of major depressive disorders, the research team looked at the diagnosis rates of all fifteen- to nineteen-year-olds across the 21 regions of Sweden, spanning a fifteen-year period from 2008. Diagnoses shot up over this timeframe. By 2022, the proportion of teenagers diagnosed with ASD had increased by a factor of five. Diagnoses of bipolar disorder had increased by a factor of 1.4, and by 2.2 for major depressive disorders.

Researchers built a statistical model from the data, finding a negative relationship between diagnosis of ASD and diagnosis of depression – depression is less likely to be diagnosed when a teenager has been diagnosed with ASD, suggesting that the latter may cloak the former. This negative relationship is particularly strong in boys.

Takeaways: the most interesting thing to jump out of this study, for me, isn’t what the researchers take from it (which is that one diagnosis may obscure another). It’s the huge spike in diagnosis rates over the fifteen years of data collection. This hasn’t happened just in Sweden. It’s an international phenomenon that’s been happening for years, as outlined in 2013 by Professor Allen Frances (who chaired the taskforce that developed the fourth version of the Diagnostic and Statistical Manual of Mental Disorders) in his excellent book Saving Normal.

Frances points out some of the huge problems that arise when we incorrectly label normal problems as mental illness, and healthy people as being mentally ill. These include stigma attached to the mislabelled individuals and less help available (financial and therapeutic support becomes thinly spread around a larger group of people) to those with more serious problems. A label isn’t always helpful.

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Cannabis is getting stronger and seems to have a serious impact on adolescent well-being

Article title: Evidence Mounting That Connects Cannabis to Youth Depression and Suicide (December 2024)

(The AI prompt got rather judgemental when I asked it to draw cannabis plants, so here are some cacti.)

‘There is mounting evidence that young people’s use of cannabis is fueling depression and suicide in this population,’ runs the punchy first line of this piece. While this is an article summarising expert opinions and the latest research, not a new academic study, we can be reasonably confident in the analysis: it’s published by Psychiatry Online, which has a number of peer-reviewed journals.

In America, the psychoactive component of cannabis – the part that creates the high – has increased from 1–3% in the 1970s to 16–25% in the 2020s. The article cites a study from 2023 that shows teenagers are more than twice as likely to suffer from major depressive disorder if they use cannabis and more than three times as likely to have had a serious episode of depression in the last year. They are also almost four times as likely to say they have attempted suicide. The more cannabis teenagers use, the greater their chances of depression and feeling suicidal.

While there’s a chance that depressed teenagers self-medicate with cannabis, other longer-term research links taking cannabis to worse future outcomes: according to one study cited in the piece, for example, using cannabis every day before the age of seventeen is linked to much higher (by a factor of almost seven) suicide attempts in adulthood. Cannabis use is particularly risky while brains are still developing.

The article cautions that the risks of cannabis aren’t fully understood by teenagers or their parents – one piece of research found that the majority of both groups believe that cannabis and CBD are ‘safe and effective mental health treatments’.

Takeaways: while lecturing is almost guaranteed to be counterproductive, teenagers need to understand the risks. Careful messaging is needed: some anti-drug campaigns in the past have normalised the idea that other teenagers take drugs and may even have led to greater drug use. (‘Everybody else is doing it? It must be worth doing, in that case.’) One thing parents can do is to avoid normalising cannabis both as it relates to wider society and, if relevant, their own histories.

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Omega-3 supplementation may support teenagers’ mental health

Study title: Omega-3 Supplementation for Adolescents and Young Adults to Combat Symptoms of Anxiety and Depression (December 2024)

This review of studies found that omega-3 supplementation is linked with a ‘modest’ reduction in depression symptoms among young adults, teenagers and younger children. Evidence was weaker on its link with symptoms of anxiety – though the research did find greater potential for dietary changes (as opposed to taking a supplement) when it comes to people feeling less anxious.

Researchers suggest that omega-3 is best as part of a ‘holistic treatment strategy’ – in other words, for those suffering serious symptoms, it’s probably not enough on its own. It is, however, safe and appears to have at least a small positive effect on teenagers experiencing poor mental health.

Takeaways: getting more omega-3 into teenagers’ diets is unlikely to hurt and is probably good for them. This is probably best done by getting food rich in omega-3 into family meals rather than encouraging them to do this for themselves. (Have you ever tried to get a teenager to change how they eat because it’s healthy? I have. It did not work.) Foods with plenty of the relevant fatty acids include fish such as salmon, tuna and sardines; nuts and seeds; and plant oils.

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