As a medical student I learned that major mental health issues often first emerge in a person’s teens and twenties. Later on I began to appreciate another peak in onset among the elderly: As a psychiatric specialist in an academic hospital I was often called in to consult on older medical and surgical patients. For many this was their first interaction with psychiatry; serious mental health concerns had never arisen in their lives before.
A few years ago I began to treat outpatients exclusively. Given previous experience I expected to see peaks in new cases among younger and older adults. So I was a bit surprised to observe yet another peak occurring at middle age. A significant portion of new patients walking into my office are between the ages of 45-55. For many it’s the first time they’ve been to see a psychiatrist, and they’re often dumbfounded to find themselves sitting in front of me. Frequently, after fidgeting awkwardly for a few minutes while trying to explain what brought them in, they will stop suddenly and ask: “Umm… Is this normal?”
Why do some people first need to see a mental health professional in their 40s and 50s? Why are there age peaks in the onset of mental health issues at all? Why do more people consult a psychiatrist for the first time when they are around 20, 50 or 70 – and not when they are 30 or 60?
As with all psychiatric questions, the answer to this one is neither purely biological nor psychological – it lies at the intersection of biology and psychology. To get an answer, let’s start by considering the peaks I mentioned in young adults and the elderly, and then we’ll get to middle age.
The usual biological explanation for why major psychiatric disorders first crop up in teenagers and twenty-somethings is that this is an age when rapid changes in brain organization occur. The brains of humans are in constant flux, but there are developmental stages when our brains undergo more sensitive adjustments than others. One such stage occurs at the transition from adolescence to adulthood. This is a time when the brain undergoes its final maturation into adult form, driven in part by a surge in sex hormones1. These hormones, along with other developmental factors, drive the final maturation or elimination of some connections (synapses) between brain cells (neurons). They also drive refinements in the branching pattern (wiring diagram) of neurons, as well as completion of the myelination (insulation) of major brain tracts (the “cables” connecting different brain regions). One theory is that some of these biological events go awry in people who first become mentally ill at this stage of their lives. Another possibility is that these developmental events occur normally in these people, but uncover biological vulnerabilities left over from earlier developmental stages. It is likely that these two theories are both correct to varying degrees in different patients.
That said, refinements in synapses and brain wiring are not the only major events happening in the lives of young adults. While this invisible biology quietly runs its course deep inside their heads, teens and twenty-somethings are also engaged in a highly conspicuous psychological and social transformation. This is the age when humans explore their first romantic relationships, bond with an intimate partner (possibly for a lifetime), seek out and establish independence from their family of origin, consider starting their own new family, and explore and choose an initial career path.
Together, these events constitute not just a sea change but a veritable tsunami of life changes. Any life change is stressful psychologically, and mental illness (like all illness) is sensitive to psychological stress. It should therefore come as no surprise that the tsunami of psychological changes occurring at the transition from adolescence to adulthood is accompanied by a peak in onset of mental health issues. It is also no coincidence that this psychologically stressful life stage coincides closely with the biological brain changes discussed in the prior paragraph. Far from being a coincidence, the psychological and biological transformations of young adulthood are two sides of the same coin. Just as you cannot separate the heads side of a coin from the tails side, you cannot separate brain biology from the psychology that surrounds it. The biological, psychological (and by extension, social and situational) shifts that occur in young adults are each a cause and consequence of the other. SOURCE