Shortly after the introduction of conventional antipsychotic drugs into clinical practice, relatively rare but serious complications with hyperthermia, muscle rigidity, autonomic instability, and disturbed mental status were recognized to develop in some patients treated with antipsychotics. This type of encephalopathy induced by the use of antipsychotics was referred to as neuroleptic malignant syndrome (NMS), and almost all physicians prescribing antipsychotics are nowadays aware of this adverse phenomenon. Another well-known type of encephalopathy associated with psychotropic drug therapy is serotonin toxicity (ST) or serotonin syndrome (SS), which is characterized by autonomic and neuromuscular symptoms and altered mental status. In contrast with the idiosyncratic nature of NMS, ST is a spectrum pathophysiological state assumed to derive from excess serotonergic neural transmission caused by serotonin-related psychotropic agents. In these two decades, pharmacotherapy with psychotropic drugs for patients with mental illness has been dramatically changed, and classical prototypal antipsychotics and antidepressants have been replaced with atypical antipsychotics and selective serotonin reuptake inhibitors (SSRIs), respectively. These newly developed psychotropic drugs are generally safer and more tolerable than older drugs. However, atypical antipsychotics are not free of the risk of development of NMS, and the explosive prevalence of SSRIs prescribed not only for depression but also for a number of psychiatric diagnoses such as anxiety, eating, impulse-control, and personality disorders may increase the incidence of ST. Therefore, these two pathological states still remain as major adverse effects of psychotropic drugs involving altered functioning of the central nervous system (CNS), to which all clinicians prescribing psychoactive drugs should pay attention.
Taylor & Francis. ISBN 9997625897. Baker, Edward L. (May 2008). "Chronic toxic encephalopathy caused by occupational solvent exposure". Annals of Neurology. 63 (5): 545–547. doi:10.1002/ana.21394. PMID 18409195. S2CID 41546628. Feldman, R G; Ratner, M H; Ptak, T (May 1999). "Chronic toxic encephalopathy in a painter exposed to mixed solvents". Environmental Health Perspectives. 107 (5): 417–422. doi:10.1289/ehp.99107417. PMC 1566426. PMID 10210698. Encephalopathy Associated with Psychotropic Drug Therapy Yuji Odagaki Department of Psychiatry, Faculty of Medicine, Saitama Medical University Department of Psychiatry, Moro Hospital Japan

External links
NINDS Encephalopathy Information Page
Encephalopathy Causes, Symptoms, Diagnosis and Treatment by MedicineNet