Explain substance-induced psychosis and follow-up to parents — CASC communication station · Psych CASC / OSCE

Prompt

Parents of a 20-year-old with first cannabis-associated psychosis want plain-language explanation of diagnosis, why medication is offered, conversion risk, cannabis advice, and whether this means lifelong schizophrenia.

Station brief

Format. Communication station, approximately 7–10 minutes active time after reading. You are the psychiatry registrar on the early intervention / acute ward. [1]

Candidate instructions. Explain the working diagnosis of substance-induced (cannabis-associated) psychosis to the parents, outline medical checks and why an antipsychotic may be used, discuss the importance of cannabis cessation, address the risk of later primary psychotic illness honestly without catastrophic fatalism, and describe the follow-up plan. Check understanding. The examiner plays both parents. [1]

Candidate scenario

Your patient, age 20, had a first episode of persecutory delusions and commentary hallucinations closely linked to daily high-THC cannabis use. Medical work-up is reassuring so far. He has started olanzapine 5 mg at night after baseline bloods and ECG. Parents ask: "Is this just drugs? Is it schizophrenia forever? Will the tablet change his personality? How long is follow-up for?" [1]

Marking domains

Empathy, structure, agenda-setting
Accurate plain-language explanation of SIP as a timeline working diagnosis
Clear medical checks and purpose of short-to-medium term antipsychotic
Honest conversion risk framed with hope and a concrete follow-up plan
Non-moralising cannabis counselling (potency/frequency; cessation as secondary prevention)
Safety-net and crisis contacts
Checks understanding [1][2][3]

Reveal assessor key

Open. Thank them; name time; ask main worries first. [1]

Explain SIP. "We think this episode of psychosis — fixed false beliefs and hearing a voice commenting — is closely linked in time to heavy high-THC cannabis use. That is sometimes called substance-induced psychosis. It is a serious medical problem, not a moral failure. We keep an open mind: some people recover fully with stopping cannabis and short-term treatment; others later need longer care for a primary psychotic illness." [1]

Why medication. Antipsychotic tablets reduce intensity of delusions and hallucinations for many people while the brain settles and cannabis use is addressed. Olanzapine at a low evening dose is one common choice; we monitor weight, glucose, lipids and ECG. Side-effects can include sedation and metabolic changes — we watch for those. It does not "erase personality" when used carefully. [1]

Conversion risk. Research (including large register studies) shows a meaningful proportion of people with substance-induced psychosis later receive diagnoses such as schizophrenia-spectrum or bipolar illness — for cannabis-linked episodes the risk sits in a high band, roughly approaching half in some long-term data, and overall about one in three across substances. That is why we do not say "just go home, it was only drugs." We also do not say on day one "this is lifelong schizophrenia forever." We plan careful follow-up. [1][2]

Cannabis. Continuing frequent high-THC use after psychosis is linked to worse course; stopping is one of the highest-yield steps he can take. Offer practical support, not shame. [3]

Follow-up. Dual plan: mental health/early intervention plus substance support, family education, early-warning signs, crisis contacts, medication review. [1]

Close. Summarise, invite questions, written information, next appointment. [1]

References

[1]Starzer MSK, Nordentoft M, Hjorthøj C Rates and Predictors of Conversion to Schizophrenia or Bipolar Disorder Following Substance-Induced Psychosis Am J Psychiatry, 2018.PMID 29179576
[2]Murrie B, Lappin J, Large M, et al. Transition of Substance-Induced, Brief, and Atypical Psychoses to Schizophrenia: A Systematic Review and Meta-analysis Schizophr Bull, 2020.PMID 31618428
[3]Schoeler T, Petros N, Di Forti M, et al. Effects of continuation, frequency, and type of cannabis use on relapse in the first 2 years after onset of psychosis: an observational study Lancet Psychiatry, 2016.PMID 27567467

Station brief

Format. Communication station, approximately 7–10 minutes active time after reading. You are the psychiatry registrar on the early intervention / acute ward. [1]

Candidate scenario

Marking domains

Empathy, structure, agenda-setting

Accurate plain-language explanation of SIP as a timeline working diagnosis

Clear medical checks and purpose of short-to-medium term antipsychotic

Honest conversion risk framed with hope and a concrete follow-up plan

Non-moralising cannabis counselling (potency/frequency; cessation as secondary prevention)

Safety-net and crisis contacts

Checks understanding [1][2][3]

Reveal assessor key

Open. Thank them; name time; ask main worries first. [1]

Cannabis. Continuing frequent high-THC use after psychosis is linked to worse course; stopping is one of the highest-yield steps he can take. Offer practical support, not shame. [3]

Follow-up. Dual plan: mental health/early intervention plus substance support, family education, early-warning signs, crisis contacts, medication review. [1]

Close. Summarise, invite questions, written information, next appointment. [1]

References

[1]Starzer MSK, Nordentoft M, Hjorthøj C Rates and Predictors of Conversion to Schizophrenia or Bipolar Disorder Following Substance-Induced Psychosis Am J Psychiatry, 2018.PMID 29179576
[2]Murrie B, Lappin J, Large M, et al. Transition of Substance-Induced, Brief, and Atypical Psychoses to Schizophrenia: A Systematic Review and Meta-analysis Schizophr Bull, 2020.PMID 31618428
[3]Schoeler T, Petros N, Di Forti M, et al. Effects of continuation, frequency, and type of cannabis use on relapse in the first 2 years after onset of psychosis: an observational study Lancet Psychiatry, 2016.PMID 27567467