[Caduceus]

Bipolar disorder and schizophrenia would most likely fit your bill.

Bipolar is the new "buzzword" as many mental health specialists think that it is underdiagnosed. Most have a depressive phase - sadness, poor energy, suicidality, with or without intruding psychoses (voices, visions). Some have a manic phase (the "bi" in bipolar) - spending sprees, sexual promiscuity, poor judgement.

Schizophrenics have walled themselves off from the world in various ways. They don't interact with stimuli that others can see and hear. They have deeply intrusive thoughts/voices and visions. Schizophrenics are more often born in the winter months, and have their first psychotic break in their late adolescence (late high school or college age) and are typically quite intelligent.

Suicide rates for both problems are much higher than the general population.