(meteorology) organized low-pressure system of thunderclouds with closed surface circulation and maximum sustained winds of less than 34 knots (63 km) per hour.

(clinical psychology, psychiatry, dated) A psychiatric diagnostic category, now called bipolar disorder, characterised by mood swings between great energy (manic) and clinical depression.

(psychology) Depression experienced by a parent, usually the mother, after childbirth.

(economics, business, finance, historical) A major economic collapse characterized by mass unemployment and limited business activity that lasted from 1929 to 1940 in the US and a similar period in many other countries.

plural of tropical depression

Alternative form of manic depression

(psychology) Winter seasonal affective disorder.

(biology) The reduced biological fitness in a given population as a result of inbreeding.

(psychology) Postpartum depression.

(psychology) The combination of depression and dysthymia.