Depressive | Disorder

Because MDD is multifactorial, no single mechanism explains every case. Leading scientific hypotheses include: Major Depressive Disorder - StatPearls - NCBI Bookshelf

: Significant changes in appetite or weight, sleep disturbances (insomnia or hypersomnia), and psychomotor agitation or retardation.

Diagnosis typically requires a persistently low mood or decreased pleasure in most activities for at least two weeks.

: Feelings of guilt or worthlessness, poor concentration, and recurrent thoughts of death or suicide.