The clinical presentation of drug-induced psychosis understands the presence of delusions and/or hallucinations [1]. Most frequent delusions are of the persecutory type, while grandiose, referential, erotomanic, nihilistic and somatic types have also been described [1]. On the other hand, an onset of vivid and clear hallucinations, either auditory (more common) or sensory, is also the main feature of psychosis [1]. The onset of symptoms significantly varies depending on the substance. For example, patients who inhale large amounts of cocaine can develop symptoms within minutes, whereas sedative-hypnotic drugs and alcohol can induce psychosis after a prolonged period of use [1] [2]. Methamphetamine and cocaine-induced psychosis typically presents with delusions of persecution and visual hallucinations that last for a short period of time, but relapses have shown to occur within one week or one month after the substance abuse [3]. A similar presentation is seen across other causes, but paranoia, distortion in the perception of time and feelings of depersonalization have been reported in patients who develop psychosis after use of hallucinogenic substances, such as cannabis or lysergic acid diethylamide (LSD) [1] [4]. Moreover, opioid intoxication is characterized by profound euphoria, while withdrawal can either lead to agitation, gastrointestinal irritation, and craving, or to depression and anhedonia [4]. Drug-induced psychosis can also occur in patients who are taking antiepileptic and antiparkinsonian drugs [5] [6], which can mislead the physician toward substance abuse.

Current diagnostic criteria of drug-induced psychosis involve the following findings [1]:

• The onset of symptoms during or soon after an introduction of a harmful substance, or exposure to a medication that can provoke such symptoms.
• An absence of other signs and symptoms that may point to another cause, including the onset of symptoms before the use of suspected drugs, a prolonged duration of complaints (about 1 month) after cessation of use, or their presence in the setting of acute withdrawal.
• Appearance of symptoms in time not related to delirium
• Significant distress and impaired daily functioning caused by symptoms.

Once a presumptive diagnosis is made, it is necessary to determine the substance that is responsible for the development of symptoms. For this reason, an adequate and thorough patient history is considered to be the most important part of the diagnostic workup, which can reveal recent use of particular medications or substances [1] [7]. Preferably, hetero-anamnestic data should be obtained, involving both the family and friends, as the patient may often refrain from admitting substance abuse. If the cause remains undetermined, routine toxicology screening of urine for recreational drugs, alcohol testing, thyroid function tests, a basic metabolic panel and a thorough workup of the central nervous system (lumbar puncture, computed tomography of the endocranium) may be performed [2] [8].

1. American Psychiatric Association. Diagnostic and statistical manual of mental disorders. Fifth Edition. Arlington, VA: American Psychiatric Publishing;2013.
2. Porter RS, Kaplan JL. Merck Manual of Diagnosis and Therapy. 19th Edition. Merck Sharp & Dohme Corp. Whitehouse Station, N.J;2011.
3. Chen Z, Lusicic A, O'Brien TJ, et al. Psychotic disorders induced by antiepileptic drugs in people with epilepsy. Brain. 2016;139(10):2668-2678
4. Paparelli A, Di Forti M, Morrison PD, Murray RM. Drug-Induced Psychosis: How to Avoid Star Gazing in Schizophrenia Research by Looking at More Obvious Sources of Light. Front Behav Neurosci. 2011;5:1.
5. Center for Substance Abuse Treatment. Substance Abuse Treatment for Persons With Co-Occurring Disorders. Rockville (MD): Substance Abuse and Mental Health Services Administration (US);2005.
6. Kuzuhara S. Drug-induced psychotic symptoms in Parkinson's disease. Problems, management and dilemma. J Neurol. 2001;248(3):III28-31.
7. Grant KM, LeVan TD, Wells SM, et al. Methamphetamine-Associated Psychosis. Journal of Neuroimmune Pharmacology. 2012;7(1):113-139.
8. Algon S, Yi J, Calkins ME, Kohler C, Borgmann-Winter KE. Evaluation and Treatment of Children and Adolescents with Psychotic Symptoms. Curr Psychiatry Rep. 2012;14(2):101-110.