Comorbidity Depression In the<unk>  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: A direct neurochemical relationship between sleep mechanisms and depression is another possibility. It is conceivable that<unk>  has a role in causing depression because it can be such a stressful and misunderstood disorder. A 2008 study from the University of California, San Diego found no association of bipolar disorder (history of mania) with<unk> , and it states that The fact that half of<unk>  patients are not depressed indicates that<unk>  is not merely a symptom of depression. Sleep researcher Michael 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.<unk>  patients who also suffer from depression may be best served by seeking treatment for both problems. There is some evidence that effectively treating<unk>  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 daylight hours (about 20 to 30 minutes three times a week, depending on skin tone, latitude, and the time of year) could be at risk, without adequate dietary sources or supplements. Attention deficit hyperactivity disorder<unk>  is genetically linked to attention deficit hyperactivity disorder by findings of polymorphism in genes in common between those apparently involved in ADHD and those involved in the circadian rhythm and a high proportion of<unk>  among those with ADHD. Overweight A 2019 study from Boston showed a relationship of evening chronotypes and greater social jet lag with greater body weight / adiposity in adolescent girls, but not boys, independent of sleep duration. Obsessive–compulsive disorder Persons with obsessive–compulsive disorder are also diagnosed with<unk>  at a much higher rate than the general public.
Delayed sleep phase disorder
Insomnia
Circadian rhythm sleep disorder
Non-24-hour sleep–wake disorder
Advanced sleep phase disorder
Shift work sleep disorder
Nightmare disorder
Rapid eye movement sleep behavior disorder