First-Episode Psychosis in a 16-Year-Old With Daily Cannabis Use
A 16-year-old sophomore is brought by his parents after a school counselor reports that he has been whispering to unseen people and accusing classmates of poisoning his lunch. For 6 weeks he has slept 3–4 hours nightly, stopped showering, and dropped from honors to failing grades. He admits to hearing two voices commenting on his actions and believes the FBI has placed a chip in his tooth. He uses cannabis daily (about 2 g), denies other drugs; urine screen is positive only for THC. He has no prior psychiatric treatment. His father has schizophrenia, and his mother is wary of 'mind-altering' medication. BMI is 31 kg/m²; vitals and basic labs are normal. He denies suicidal or homicidal ideation but says he might 'have to defend myself.' The family has insurance but limited transportation and lives 90 minutes from the clinic.
1. What is your differential diagnosis, and how would you prioritize it during the first visit?
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The differential includes a primary psychotic disorder (schizophrenia spectrum or bipolar I with psychotic features), cannabis-induced psychosis, and a medical or toxic cause. The 6-week duration with functional decline, commenting auditory hallucinations, and a first-degree relative with schizophrenia raise the probability of a primary psychotic disorder, but daily cannabis use must be addressed rather than dismissed. I would obtain a careful timeline: whether psychosis began before or after cannabis, whether it persists during abstinence, and whether there are manic symptoms. I would check vitals, urine toxicology, TSH, CBC, CMP, and consider MRI or EEG if focal signs or atypical features appear. I would not make a definitive diagnosis at the first visit; I would use a provisional diagnosis and reassess after 2–4 weeks of abstinence and treatment. The parent's reluctance means I would explain that cannabis may worsen psychosis but does not rule out a primary disorder. This is a judgment about probabilistic reasoning, not a single test.
2. How do you assess risk and choose a level of care?
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The statement that he 'might have to defend myself' requires direct follow-up: Does he mean retaliating against classmates? Does he have a specific target, plan, weapon access, or command hallucination telling him to act? I would ask about suicide, aggression, and access to firearms, and I would ask the parents separately. If there is a specific threat, command hallucination, or weapon access, inpatient admission is indicated for safety and stabilization. If not, intensive outpatient or partial hospital care with daily monitoring may be appropriate, but the 90-minute distance and transportation barriers make adherence fragile. I would consider a brief inpatient stay for diagnostic clarification and family engagement even without imminent danger. Legal hold criteria vary, but the clinical principle is the least restrictive setting that can manage risk. I would document the risk assessment, safety plan, and rationale, and involve the school counselor for monitoring.
3. How would you negotiate pharmacologic treatment with a parent who prefers 'natural' approaches, and what monitoring would you set up?
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I would start with alliance and curiosity: what does 'natural' mean to her, what are her fears, and what has she read? I would explain that untreated first-episode psychosis carries risks of violence, school loss, and prolonged recovery, and that antipsychotics reduce relapse. I would present a second-generation antipsychotic such as aripiprazole or risperidone, start low, and explain target symptoms and side effects. Shared decision-making does not require agreement on everything; I can offer a time-limited trial with clear benchmarks. I would not hide treatment or override assent unless emergency. Monitoring includes BMI, waist circumference, blood pressure, fasting glucose or A1c, and lipids at baseline and 3 months; EPS and akathisia; prolactin if risperidone; and sedation. I would add family psychoeducation, cannabis cessation, school accommodations, and coordinated follow-up. If the parent refuses all medication and danger escalates, I would involve child protective services or emergency services as legally required.