Dysthymia, Cyclothymia & SAD

Key points

• Dysthymia (persistent depressive disorder): chronic low mood ≥ 2 years, not meeting full depressive episode criteria.
• Cyclothymia: chronic fluctuating mood with hypomanic and sub-depressive periods ≥ 2 years.
• Seasonal affective disorder: recurrent winter depression with hypersomnia and carbohydrate craving; treated with light therapy and SSRIs.
• SAD: more common in higher latitudes; linked to melatonin/serotonin dysregulation.