Anxiety, depression and other mental disorders are fairly common.  At some point a majority of us will experience some form of mental illness, if only for a short time.
D001294:Attitude to Health; D006801:Humans; D008137:Longitudinal Studies; D001523:Mental Disorders / Q000453:epidemiology*; D009520:New Zealand / Q000453:epidemiology; D018570:Risk Assessment