sads

Seasonal affective disorders (SADs), commonly called seasonal affective disorder, are depressive disorders with a seasonal pattern. Depressive episodes most often begin in fall or winter and remit in spring or summer, though a minority have a summer onset. The seasonal pattern may be mild or subclinical in between seasons.

Symptoms typically include persistent low mood, loss of interest or pleasure, fatigue, sleep disturbance, changes in appetite or weight, difficulty concentrating, and social withdrawal. The winter form is often accompanied by hypersomnia and carbohydrate cravings, while the summer form may involve insomnia and poor appetite. These symptoms can impair daily functioning and tend to recur each season.

Causes involve changes in daylight that disrupt circadian rhythms and signaling of serotonin and melatonin. Risk factors include higher latitude, family history, prior depressive episodes, and younger age. SAD appears more commonly in women in some studies, though prevalence varies by population.

Diagnosis is clinical. In DSM-5, a seasonal pattern specifier is applied when depressive episodes tend to recur in a seasonal pattern, typically over several years, after other medical or psychiatric causes are ruled out.

Treatment options include light therapy, typically about 20–30 minutes of bright light daily in the morning (around 10,000 lux), psychotherapy such as cognitive-behavioral therapy, and antidepressants, commonly selective serotonin reuptake inhibitors. Vitamin D supplementation is used in some cases, but evidence for routine use is mixed. Lifestyle measures such as regular exercise, stable sleep routines, and outdoor activity can support improvement.

Prognosis varies, but many respond to treatment, and episodes may recur in future winters. SAD is more prevalent at higher latitudes due to reduced winter daylight.