From the Research: Seasonality of Brain Function & Relapse Risk
Ask any clinician who’s been in the field for a while whether they see more crises in certain parts of the year and you’ll get a knowing look before you finish the sentence. The late-winter slide. The holiday drop-off. The first warm week of spring when everything feels brittle. For a long time that was clinical folklore. The last decade of neuroscience is starting to show that it’s also real biology.
What the researchers looked at
Ruiyi Zhang and Nora Volkow — Volkow being the longtime director of the National Institute on Drug Abuse — published a review in Nature’s Translational Psychiatry pulling together evidence on how the human brain varies across seasons, and what that variation means for psychiatric disorders including depression, anxiety, suicide risk, and substance use. They looked at imaging studies, transmitter chemistry, circadian and sleep-regulation data, light-exposure effects, and epidemiological patterns.
What they found
Brain chemistry is not a stable baseline you return to all year long. Key systems involved in mood, motivation, and reward show measurable seasonal variation. Serotonin transporter availability shifts across the year. Dopamine signaling is sensitive to daylight and sleep cycles. Stress reactivity moves with the seasons, too. Those shifts show up in the outside world as seasonal patterns in depression, anxiety, suicide rates, and, yes, substance use crises. The authors are careful — they don’t claim the seasons cause relapse. What they show is that the brain you’re bringing to recovery in February is a somewhat different brain than the one you were working with in July.
The part that I think matters most for peer and clinical work is that this is information you can plan around. You can schedule extra contact during the time of year a client historically struggles most. You can front-load supports in the weeks before a predictable trigger window. You can be ready, instead of surprised.
Why this matters for families
Families often feel blindsided when a loved one does well for months and then slides during a specific part of the year. It’s easy to interpret that as a character failure or a secret relapse that was hiding all along. It may not be either. Some of it is the calendar itself pulling on a nervous system that hasn’t fully recovered yet. Understanding that reframes the question. Instead of “why did this happen?” it becomes “which season is hardest for them, and what does support look like next time we get close to it?”
Key Takeaways
Human brain chemistry genuinely varies across the year — mood, motivation, stress, and reward systems all shift.
Seasonal changes in neurotransmitter systems correlate with seasonal changes in psychiatric risk, including substance-use crises.
This isn’t fate; it’s information. Anticipating the hard season lets you plan supports ahead of it instead of reacting after.
Families should know a loved one’s historical “hard window” and protect it the way you’d protect any other vulnerability.
Clinicians and coaches can and should build seasonality into recovery planning rather than treating the year as flat.
Source: Zhang, R., & Volkow, N. D. Translational Psychiatry (2023). Read the full study →