Delayed Sleep Phase Disorder - Comorbidity

Comorbidity

In the DSPD cases reported in the literature, about half of the patients have suffered from clinical depression or other psychological problems, about the same proportion as among patients with chronic insomnia. According to the ICSD:

Although some degree of psychopathology is present in about half of adult patients with DSPD, there appears to be no particular psychiatric diagnostic category into which these patients fall. Psychopathology is not particularly more common in DSPD patients compared to patients with other forms of "insomnia." ... Whether DSPD results directly in clinical depression, or vice versa, is unknown, but many patients express considerable despair and hopelessness over sleeping normally again.

A direct neurochemical relationship between sleep mechanisms and depression is another possibility. DSPD may cause excessive or inappropriate production of melatonin. Serotonin, a mood regulator, is a precursor to melatonin. As a result, increased endogenous melatonin production can deplete serotonin levels and may cause depression.

It is conceivable that DSPD often has a major role in causing depression because it can be such a stressful and misunderstood disorder. A recent study from the University of California, San Diego found no association of bipolar disorder (history of mania) with DSPD, and it states that there may be

behaviorally-mediated mechanisms for comorbidity between DSPS and depression. For example, the lateness of DSPS cases and their unusual hours may lead to social opprobrium and rejection, which might be depressing...

The fact that half of DSPD patients are not depressed indicates that DSPD is not merely a symptom of depression. Sleep researcher M. Terman has suggested that those who follow their internal circadian clocks may be less likely to suffer from depression than those trying to live on a different schedule.

DSPD patients who also suffer from depression may be best served by seeking treatment for both problems. There is some evidence that effectively treating DSPD can improve the patient's mood and make antidepressants more effective.

Vitamin D deficiency has been linked to depression. As it is a condition which comes from lack of exposure to sunlight, anyone who does not get enough sunlight exposure during the daylight hours could be at risk.

Persons with obsessive-compulsive disorder are also diagnosed with DSPD at a much higher rate than the general public.