bipolar /ˌbaɪˈpəʊlə(r)/ (disorder): a mental illness causing somebody to change suddenly from being extremely depressed to being extremely happy
anorexia /ˌænəˈreksiə/: an emotional disorder, especially affecting young women, in which there is an abnormal fear of being fat, causing the person to stop eating, leading to dangerous weight loss
phobia /ˈfəʊbiə/: a strong unreasonable fear of something
schizophrenia /ˌskɪtsəˈfriːniə/: a mental illness in which a person becomes unable to link thought, emotion and behaviour, leading to withdrawal from reality and personal relationships
bulimia /buˈlɪmiə/: an emotional disorder in which a person repeatedly eats too much and then forces him- or herself to vomit
kleptomania /ˌkleptəˈmeɪniə/: a mental illness in which somebody has a strong desire, which they cannot control, to steal things
dementia /dɪˈmenʃə/: a serious mental disorder caused by brain disease or injury, that affects the ability to think, remember and behave normally
paranoia /ˌpærəˈnɔɪə/: a mental illness in which a person wrongly believes that other people are trying to harm them, that they are somebody very important, etc.
Hallucination /həˌluːsɪˈneɪʃn/: the fact of seeming to see or hear somebody/something that is not really there, especially because of illness or drugs
delusion /dɪˈluːʒn/: a false belief or opinion about yourself or your situation situation