The interaction between sleep and mood is fascinating, complex and supremely practical.
I have received a couple of queries and comments. Let me start with one from a physician:
“I have a question about sleep disorders. My patients seem to suffer from this even after their depression is better.”
This is an extremely interesting issue.
Every healthcare student has been taught about the sleep disturbances that may occur in association with mood disorders. The classic problems in depression are early morning wakening, difficulty in getting off to sleep and sometimes waking in the early hours. Some others will sleep for very long periods, and there has been speculation that this may be a form of hibernation behavior. People with abnormally elevated mood can often stay awake for days at a time. There is also the well-known problem of seasonal affective disorder, in which the long winter nights can cause depression. Fortunately the depression is often relieved by the use of a light box.
Many experts now consider that the disturbances of sleep are often the primary problem, which then cause depressed or elevated mood. This is actually not a new idea: one of the old fashioned treatments for depression was sleep deprivation and many of us who have worked all night have experienced the mildly manic symptoms of sleep deprivation. On early morning rounds at the hospital I commented that it was easy to tell if some of the residents had been working all night, even before they presented their reports. The giggling, high energy and disturbances in thought patterns were not at all what one sees when someone is tired.
It is not just the sleep deprivation, but also light. It is well known that people suffering with bipolar disorder are more likely to get manic episode in the spring and early summer, as the amount of ambient light increases. It is the converse of the seasonal affective disorder problem.
So what often happens is that antidepressant medications do indeed help with the depressed mood, but the underlying sleep problem takes much longer to correct itself. This is also one of the reasons why people who have seen their mood improve on treatment still have cognitive problems that can go on for months after the mood symptoms have been corrected. It is probably a combination of sleep deprivation and also the impact of corticosteroids that can rise in some sufferers causing transient damage to some key regions of the brain.
It would be nice if we could modulate people’s sleep/wake cycles and thereby treat the mood problems directly, but at the moment, despite the enormous advances in pharmacological treatments of sleep problems, we are still not able to do that reliably.