Understandable (such as bereavement, major stresses)
Neurotic (high anxiety personalities, negative parental upbringing)
Hypochondriasis
Agitation (usually organic causes such as dementia)
Pseudodementia
Pain
Importuniing (whingeing, complaining)
Nihilistic
Endogenous
Secondary (i.e. cancer at the head of the pancreas, bronchogenic cancer)
Syndromal

 Mnemonic:
UNHAPPINESS