In people diagnosed as having a mood disorder the moods last a long time, colour all their interactions with the world and disrupt their normal functioning. In depression the person suffers recurrent depression but has no history of mania. Bipolar disorder entails alternating periods of depression and mania, usually with intervening periods of normal mood. Most bipolar mood disorders begin with a manic episode. The symptoms of depression include emotional sadness, loss of pleasure from anything, lack of affection for other people, lack of motivation, dramatic decreases in activity, slow, quiet speech and movements, reduced eye contact with others, thinking of oneself as a failure and physically unattractive, and blaming oneself for almost everything.
Confusion is common, although no intellectual impairment seems to occur.
Physical symptoms such as insomnia and changes in appetite may also appear. Because depressed people focus inwardly, they may also magnify physical aches and pains. Just reading through this list I can tick almost every characteristic as applying to Nick. In contrast, during a manic episode people feel euphoric and jovial, although the joy is out of all proportion to what is happening in their lives. They are driven, impulsive, extremely talkative, desire constant excitement and companionship, but do not realise they seem overwhelming to other people.