The paper Hedonistic homeostatic dysregulation in patients with Parkinson's disease on dopamine replacement therapies by Giovannoni et al in this issue of the Journal (pp 423-8)¹ provides an important new perspective on the neurobiology of addiction.

These investigators have studied a small number of patients with Parkinson's disease who develop features of addiction to dopamine replacement therapy. The patients were mostly men with early onset Parkinson's disease responsive to dopaminergic therapy. They showed an increasing need for dopaminergic treatment in excess of that normally required to relieve parkinsonian signs and symptoms. The patients developed marked dyskinesias and felt "on" only during dyskinetic periods; they developed behaviours typical of drug dependent patients including drug seeking, drug hoarding, an unwillingness to reduce dopaminergic therapy, and accelerating increases in the amount of dopaminergic treatment used. The addiction produced impairment in social and occupational functioning with violent behaviour, interruption of marital relations and . . . [Full text of this article]