Coignoux 2009.

Methods	A patient report of ADHD and schizophrenia during methylphenidate treatment
Participants	Diagnosis of ADHD: DSM‐IV (subtype: hyperactive‐impulsive) Age: 14 years old IQ: 135 Sex: male Ethnicity: white Country: France Comorbidity: schizotypal personality disorder, infantile psychosis with schizophrenia, OD, CDD Comedication: risperidone Sociodemographics: high cultural level
Interventions	Methylphenidate type: extended release Methylphenidate dosage: 54 mg/day Administration schedule: once daily, morning Duration of treatment: 2 years Treatment compliance: not stated
Outcomes	Serious adverse events: Development of gestural stereotypes and verbal aggressiveness towards his parents on methylphenidate treatment. After 6 months 4 mg risperidone is introduced. He improves, gets a less vindictive attitude but there remains some ritualised obsessive, defensive behaviour. His IQ has dropped 20 points
Notes	Funding/vested interest: none Authors' affiliations: none Key conclusions of the study authors: this study revealed the limits of category‐based approach and international classifications as they do not express clinical singularities or possible neurobiological continuums. It also seems to confirm the possible risk of emergence of a psychosis for schizotypal participants, due to pharmaceutical induction by psychostimulants (methylphenidate). This emergence could be stopped by a combined antipsychotic treatment Comments from the study authors: in our case, the cognitive exploration was not precise enough to conclude, but emphasize that the negative development of IQ in the patient illustrates quite well the assumption of risk of change in adolescents with a significant and sharp decline in IQ to a psychotic disorder in adulthood Comments from the review authors: the authors state that methylphenidate might have induced the psychosis ‐ and therefore the patient report is included despite polypharmacy