About This Page
This is a clinician-written, evidence-based guide aligned to the MCC Examination Objectives. It is structured by clinical presentation — the way the MCCQE tests and the way patients actually present. Management reflects current Canadian guidelines (CMA, CFPC, CPS). Always cross-reference with institutional protocols and clinical judgment.
The Bottom Line
- ADHD is a clinical diagnosis requiring persistent inattention and/or hyperactivity-impulsivity, childhood onset, impairment, and symptoms in more than one setting
- The differential is broad: sleep deprivation/OSA, anxiety, depression, trauma, substance use, learning disorder, autism, mania, thyroid disease, seizures, and normal developmental variation
- Collateral is essential: parent/teacher reports for children; school records, partner/family, and childhood history for adults
- Treatment combines psychoeducation, behavioural/academic/workplace supports, and medication when impairment is significant
- Do not diagnose ADHD from a questionnaire alone; rating scales support but do not replace a structured developmental and differential assessment
Approach to the Presentation
Inattention and hyperactivity commonly present as poor school performance, disruptive behaviour, procrastination, emotional dysregulation, forgetfulness, impulsive decisions, driving problems, or workplace underperformance. Ask when symptoms began, whether they occur at school/work/home, whether impairment is chronic or recent, and what changed. Obtain collateral and screen for sleep problems, anxiety, depression, trauma, substance use, learning disability, autism, hearing/vision problems, seizures, thyroid symptoms, and family stress. In adults, confirm childhood onset and avoid diagnosing ADHD solely from current productivity difficulties or stimulant response.
Differential Diagnosis
| diagnosis | likelihood | key features | distinguishing test |
|---|---|---|---|
| Bipolar disorder / mania | must-not-miss | Episodic decreased need for sleep, increased energy, grandiosity, pressured speech, risky behaviour; may be mistaken for hyperactivity/impulsivity | Longitudinal mood history and collateral; symptoms episodic rather than lifelong |
| Substance use or stimulant/cannabis effects | must-not-miss | Cannabis-related amotivation, stimulant misuse, cocaine/amphetamine use, alcohol/sedative effects, withdrawal, diversion-seeking | Substance history, collateral, prescription monitoring where available, urine tox if indicated |
| Sleep disorder / obstructive sleep apnoea | common | Insomnia, insufficient sleep, snoring, restless sleep; children may show hyperactivity rather than sleepiness | Sleep history, sleep diary, STOP-Bang, sleep study if indicated |
| Anxiety disorder | common | Poor concentration due to worry, perfectionism, avoidance, panic, somatic anxiety; attention worse during stress | GAD-7/clinical anxiety assessment |
| Depression | common | Low motivation, poor concentration, fatigue, psychomotor slowing, sleep/appetite change, anhedonia | PHQ-9 and mood history |
| ADHD | common | Persistent inattention, disorganisation, forgetfulness, impulsivity, restlessness, emotional dysregulation since childhood with impairment in multiple settings | Clinical DSM-5-TR criteria + collateral + rating scales |
| Learning disorder / intellectual disability | common | Inattention specific to reading, writing, math, or tasks above ability level; academic discrepancy | Psychoeducational assessment, school records |
| Autism spectrum disorder | less common | Social communication differences, restricted interests, sensory sensitivities, rigidity; ADHD commonly comorbid | Developmental history and autism assessment |
| Trauma / adverse childhood experiences | less common | Hypervigilance, dissociation, irritability, concentration difficulties after trauma | Trauma-informed history; PTSD screen |
| Medical causes | less common | Thyroid disease, anaemia, absence seizures, hearing/vision impairment, medication effects | Targeted exam/labs; vision/hearing testing; EEG if indicated |
Red Flags & Key History
Symptoms
Episodic reduced need for sleep with high energy, grandiosity, or risky behaviour
Psychosis, suicidality, severe aggression, or major functional collapse
New onset in adulthood without childhood history — look for mood, sleep, substance, medical causes
Chest pain, syncope, known structural heart disease, or family history of sudden death before stimulant therapy
Diversion, stimulant misuse, or active substance use disorder
Impairment across home/school/work, chronic disorganisation, forgetfulness, impulsivity
Signs
Hyperactivity/restlessness with normal mood and chronic developmental pattern
Thyroid signs, neurological signs, absence spells, or hearing/vision concerns
Elevated BP/HR before stimulant initiation
Signs of intoxication, withdrawal, or sleep deprivation
Approach to Investigation
First-line
Developmental and impairment historyAge of onset, symptoms before age 12, impairment in at least two settings, school/work records, family history, and functional consequences
Collateral reports and rating scalesParent/teacher scales for children; adult ADHD scales plus childhood collateral for adults
Differential screenSleep, anxiety, depression, mania, trauma, substance use, learning disorder, autism, medical/medication causes
Baseline physical assessment before medicationBP, HR, weight/BMI, cardiac history, family history of sudden death; ECG only when cardiac risk suggests
Second-line
Psychoeducational testingWhen learning disorder, intellectual disability, giftedness/underchallenge, or school accommodation needs are unclear
Targeted medical testsTSH, CBC/ferritin, sleep study, hearing/vision testing, EEG only when clinical features suggest
Specialist
Paediatrics/psychiatry/psychology referralDiagnostic complexity, severe comorbidity, preschool age, autism/ID, bipolar/psychosis concern, substance misuse, or treatment failure
School/work accommodation assessmentIndividual education plan, disability office, occupational strategies, coaching, and environmental modifications
Management Principles
CADDRA Canadian ADHD Practice Guidelines + CADDRA Medication Chart + DSM-5-TR1
Psychoeducation and supports
- Explain ADHD as a neurodevelopmental disorder affecting executive function, not laziness
- Behavioural parent training, classroom strategies, routines, sleep regularity, exercise, reduced distractions, organisational coaching, and academic/work accommodations
- Treat sleep, anxiety, depression, trauma, and substance use because they can mimic or worsen ADHD
2
Medication principles
- Stimulants are first-line for many patients: methylphenidate or amphetamine formulations; choose based on duration needed, adverse effects, cost/coverage, and misuse risk
- Non-stimulants include atomoxetine, guanfacine XR, and clonidine XR in selected cases
- Monitor BP/HR, weight/appetite, sleep, mood, tics, misuse/diversion, and functional goals
3
Safety and comorbidity
- Do not start stimulants in uncontrolled mania, psychosis, severe substance use instability, or unassessed significant cardiac risk
- If anxiety/depression is primary and recent, treat that first; if ADHD is primary and chronic, treating ADHD may improve secondary anxiety
Complications & Pitfalls
- Questionnaire-only diagnosis: ADHD requires clinical assessment, impairment, childhood onset, and collateral where possible.
- Adult new-onset trap: New concentration problems in adulthood are more often sleep, mood, anxiety, substance, or medical causes.
- Missing mania: Stimulants can worsen mania/psychosis.
- Ignoring learning disorder: A child may look inattentive because the work is inaccessible.
MCCQE1 Exam Tips
- 1ADHD must cause impairment in more than one setting and begin in childhood
- 2Rating scales support diagnosis but do not replace collateral and clinical assessment
- 3Sleep deprivation/OSA, anxiety, depression, trauma, and substance use are high-yield ADHD mimics
- 4Before stimulants: check BP/HR, cardiac history, family sudden death history, and substance misuse risk
- 5Mania is episodic; ADHD is chronic/developmental. Decreased need for sleep points away from simple ADHD
- 6CADDRA is the Canadian guideline anchor for ADHD assessment and medication choices
practicetest your knowledge on inattention & hyperactivity (adhd approach)Apply what you've learnt with MCCQE1-style questions from the iatroX Q-Bank — psychiatric and beyond.
open q-bank