9.2 Mental Health & Behavioural Science

Why Mental Health Is in the Part 1 Syllabus

Outcome C5.1 requires knowledge of common mental health problems and B1.7 places mental health inside common medical problems. Around one adult in four experiences a mental health problem in any year, so this is not a niche topic — and the dental consequences arise as much from medication and self-care as from the illness itself.

Common Conditions and Their Dental Relevance

Drug interactions that matter to a dentist

• Lithium and NSAIDs — NSAIDs reduce renal lithium clearance and can precipitate toxicity (tremor, ataxia, confusion). Use paracetamol; if an NSAID is unavoidable, liaise with the prescriber and arrange level monitoring.
• SSRIs with NSAIDs or aspirin — additive gastrointestinal bleeding risk; SSRIs also mildly impair platelet function.
• SSRIs and tramadol — serotonin syndrome and a lowered seizure threshold; avoid the combination.
• Tricyclic antidepressants — pronounced xerostomia and postural hypotension; adrenaline-containing local anaesthetic in normal doses with aspiration is acceptable, but avoid large volumes.
• Monoamine oxidase inhibitors — avoid pethidine; standard doses of dental local anaesthetic with adrenaline are not contraindicated, but excessive doses should be avoided.
• Antipsychotics — xerostomia, tardive dyskinesia complicating impressions and denture wear, and QT prolongation with some agents, which matters when other QT-prolonging drugs are added.
• Clozapine — hypersalivation rather than dry mouth, plus a risk of agranulocytosis: unexplained oral ulceration, sore throat or infection in a clozapine patient warrants an urgent full blood count and same-day medical advice.

Approaching a suspected eating disorder

Erosion confined to the palatal surfaces of the upper anterior teeth in a young patient, with parotid swelling and no dietary acid source, should prompt a non-confrontational conversation. Describe what you can see, ask openly about reflux and vomiting, advise against brushing immediately after vomiting (rinse with water or a fluoride mouthrinse and wait), prescribe high-fluoride toothpaste, and offer to help the patient reach their GP or an eating disorder service. Confrontation and moralising reliably end both the conversation and the attendance.

Behavioural Science (Outcome C5.3)

Behavioural science explains why telling people what to do rarely changes what they do.

The transtheoretical (stages of change) model

Giving a precontemplative smoker a quit date fails because the intervention is mismatched to the stage; the same advice at the preparation stage succeeds.

Motivational interviewing

A collaborative, guiding style built on open questions, affirmations, reflective listening and summarising. It works by eliciting change talk from the patient rather than supplying arguments, and it deliberately suppresses the "righting reflex" — the clinician's instinct to correct and persuade, which reliably provokes resistance.

Other models worth recognising

• Health belief model — behaviour depends on perceived susceptibility, perceived severity, perceived benefits, perceived barriers, cues to action and self-efficacy. Perceived barriers are usually the strongest single predictor of whether a patient acts.
• Social cognitive theory — self-efficacy, observational learning and reinforcement; the theoretical basis of modelling and tell–show–do.
• Classical and operant conditioning — how one painful early visit becomes lifelong avoidance, and how graded exposure with positive reinforcement can unlearn it.
• Nudge and choice architecture — sugar-free medicines by default, water as the default drink in schools; population behaviour change without individual persuasion.