major affective disorder

NOUN
24 LETTERS · STARTS WITH M

major affective disorder is a valid 24-letter word worth 44 points in Scrabble and 49 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS
M3A1J8O1R1A1F4F4E1C3T1I1V4E1D2I1S1O1R1D2E1R1
3 + 1 + 8 + 1 + 1 + 0 + 1 + 4 + 4 + 1 + 3 + 1 + 1 + 4 + 1 + 0 + 2 + 1 + 1 + 1 + 1 + 2 + 1 + 1 =44 PTS
DOUBLE WORD → 88TRIPLE WORD → 132
MEANING

What does major affective disorder mean?