In 1992, psychiatrist Richard Bentall wrote an article in the Journal of Medical Ethics proposing that happiness be classified as a psychiatric disorder. Here's his abstract:

It is proposed that happiness be classified as a psychiatric disorder and be included in future editions of the major diagnostic manuals under the new name: major affective disorder, pleasant type. In a review of the relevant literature it is shown that happiness is statistically abnormal, consists of a discrete cluster of symptoms, is associated with a range of cognitive abnormalities, and probably reflects the abnormal functioning of the central nervous system. One possible objection to this proposal remains--that happiness is not negatively valued. However, this objection is dismissed as scientifically irrelevant.

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