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Anhedonia ( ; Greek: ἀν- ''an''-, "without" and ἡδονή ''hēdonē'', "pleasure") is defined as the inability to experience pleasure from activities usually found enjoyable, e.g. exercise, hobbies, music, sexual activities or social interactions. While earlier definitions of anhedonia emphasized pleasurable experience, more recent models have highlighted the need to consider different aspects of enjoyable behavior, such as motivation or desire to engage in activities (motivational anhedonia), as compared to the level of enjoyment of the activity itself ("consummatory anhedonia"). According to William James the term was coined by Théodule-Armand Ribot. One can distinguish many kinds of pathological depression. Sometimes it is mere passive joylessness and dreariness, discouragement, dejection, lack of taste and zest and spring. Professor Ribot proposed the name anhedonia to designate this condition. "The state of anhedonia, if I may coin a new word to pair off with analgesia," he writes, "has been very little studied, but it exists."〔''Varieties of Religious Experience'' Lecture VI, The Sick Soul, William James 1902〕 Anhedonia can be a characteristic of mental disorders including mood disorders, schizoaffective disorder, borderline personality disorder, schizoid personality disorder and schizophrenia. For example, the 7th DSM-IV criterion for Borderline Personality Disorder: "chronic feelings of emptiness." Results indicate that emptiness is negligibly related to boredom, is closely related to feeling hopeless, pathologically lonely, and isolated, and is a robust predictor of depression and suicidal ideation (but not anxiety or suicide attempts). Findings are consistent with DSM-IV revisions regarding the 7th criterion for Borderline Personality Disorder. In addition, findings suggest the emptiness reflects pathologically low positive affect and significant psychiatric distress. People affected with schizophrenia often describe themselves as feeling emotionally empty.〔Hales R., Yudofsky S., Talbott J. 1999. Textbook of Psychiatry 3rd ed. Washington DC: The American Psychiatric Press.〕 Mood disturbances are commonly observed in many psychiatric disorders. Disturbing mood changes may occur resultant to stressful life events and they are not uncommon during times of physical illness. While anhedonia can be a feature of such mood changes, they are not mutually inclusive. ==Causes== Researchers theorize that anhedonia may result from the breakdown in the brain's reward system, involving the neurotransmitter dopamine. Studies by Paul Keedwell, MD, then of King's College, found that the brains of participants who were clinically depressed had to work harder to process rewarding experiences.〔John McManamy, ("No Pleasure, No Reward – Plenty of Depression" ), URL accessed 2009-02-17〕 While earlier research believed dopamine to be primarily involved in the subjective experience of pleasure, the last 20 years has seen a conceptual shift, such that dopamine is now believed to underlie various aspects of reward anticipation, learning, and motivation. Anhedonia can be characterised as "impaired ability to pursue, experience and/or learn about pleasure, which is often, but not always accessible to conscious awareness".〔https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4356228/〕 Anhedonia is also a relatively common side effect of antidopaminergic neuroleptics or antipsychotic drugs, as well a side effect of withdrawal from stimulants such as phenethylamines, or amphetamines. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Anhedonia」の詳細全文を読む スポンサード リンク
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