Explain adolescent cannabis use disorder and the cannabis-psychosis question to parents — OSCE

Candidate instructions

You are the paediatric registrar. The parents of a 16-year-old boy with daily cannabis use since age 13, falling school marks and a new risky peer group have ten minutes with you. They have read online that cannabis causes psychosis and are frightened, and they blame themselves. Explain, in plain language: (1) what a cannabis use disorder is and that it is a treatable condition, not a character flaw; (2) how the diagnosis is made on a pattern of symptoms, not a drug test; (3) what treatment looks like and why it works; and (4) an honest, balanced account of the cannabis-and-psychosis evidence and how you will monitor his mental health. Invite their questions and agree a shared plan. Do not lecture; check understanding throughout. [2]

Encounter

Parent: "He's been smoking every day since he was thirteen and his marks have collapsed. Is he just going to end up psychotic? What have we done wrong?" [4]

Registrar: "I can hear how frightening and heavy this is, and I want you to know this is not your fault and it is not a character flaw in him. What he has is a recognised, treatable medical condition — a cannabis use disorder. It is a pattern where the use has started to take over: he cannot easily cut down, it is affecting school and friendships, and he is using in risky ways. The good news is we have treatments that work for exactly this." [2]

Parent: "But how do you know it is a disorder and not just him being a teenager?" [1]

Registrar: "We diagnose it from a careful conversation about a set pattern of symptoms — things like failed efforts to cut down, use getting in the way of school and friends, using in risky situations like driving, and withdrawal when he stops. It is not diagnosed from a urine test, and it is not about how much he uses on one day. He is meeting several of those criteria, which is why we call it a disorder and why treatment is warranted." [1]

Parent: "What does treatment actually look like?" [3]

Registrar: "The strongest evidence for teenagers is talking therapy. We use motivational interviewing, which means meeting him where he is rather than lecturing him, then cognitive behavioural therapy and family-based work to help him recognise triggers and build skills. Studies of cannabis treatment in teenagers — including a large one called the Cannabis Youth Treatment study — show these approaches reduce use and improve outcomes. We also treat the things that travel with it, like his low mood, and we give him a clear person to follow up with. It is not a quick fix, and the path is not always a straight line, but it works." [3]

Parent: "And the psychosis thing — is he going to lose his mind?" [4]

Registrar: "Let me give you the honest picture. There is good evidence that the earlier and the heavier the cannabis use, especially strong forms of it, the higher the chance of mental-health problems later, including psychotic symptoms. So we take it seriously — we will help him reduce and stop, and we will monitor his mood and thinking regularly. But it is not a certainty — most young people who use cannabis do not develop psychosis. What matters is that we act now, reduce the use, and keep a close eye on him. If he ever had persistent odd thoughts or heard things that were not there, we would see it and step in quickly." [4]

Parent: "So what happens next?" [2]

Registrar: "I would like to refer him to our youth alcohol-and-other-drug service, where a team he can trust will build a plan with him — therapy, family support, and a follow-up clinician whose name he knows. I will also see him back here to keep an eye on his mood and his school engagement. Before we finish, I want to agree the plan with you and with him, and to remind you that this is a marathon, not a sprint — relapses can happen and they are not failures, they are part of the course we manage together. What questions do you still have?" [2]

Marking domains

• Communication (25%): plain language, empathy, checks understanding, invites questions, avoids jargon and a moralising or punitive tone.
• Clinical content (30%): explains a cannabis use disorder as a treatable, criteria-based condition; describes how the diagnosis is made on symptoms rather than a drug test; outlines evidence-based psychosocial therapy (CBT, family-based, motivational interviewing) citing the treatment evidence. [3]
• Shared decision-making (20%): presents the plan as collaborative; acknowledges the family's fear and guilt; agrees a written plan and a clear follow-up.
• Safety and monitoring (15%): gives a balanced account of the cannabis-and-psychosis evidence; names the warning signs that need urgent review and the monitoring plan.
• Professionalism and global (10%): maintains a non-judgemental, strength-based, recovery-oriented stance; appropriate confidentiality with carer involvement.