Dr Regu logo Dr ReguClinical Library Browse the Library
Home / Library / Clinical Pathways / ADHD Diagnostic Algorithm & Comorbidity
Clinical Pathway

ADHD — Diagnostic Algorithm & Comorbidity

Specialist's 5-step pathway & mandatory comorbidity checks

Field: Mental HealthCode: MH-01CUpdated: June 2026Reference: AADPA Clinical Practice Guideline
The specialist confirms the diagnosis; your role is the comorbidity screen. Anxiety, depression, bipolar disorder and substance use disorder are common alongside ADHD and change what happens next — screen for all four before or alongside referral.

5-step diagnostic algorithm

Specialist-led; systematic, not self-report alone.

1
Symptoms: confirm ≥6 (≥5 if 17+) symptoms for ≥6 months using the DSM-5-TR checklist systematically — collateral history is essential, not optional.
2
Chronicity & settings: ≥2 settings (e.g. home and school/work); some symptoms present before age 12 — school reports give the most compelling evidence.
3
Functional impairment: quantify it — falling grades, job loss, relationship breakdown, missed appointments; impairment is what separates disorder from trait.
4
Rule out other causes: did symptoms clearly predate any mood episode, psychosis or substance use? Autism, anxiety, depression, bipolar disorder and trauma can all overlap.
5
Severity: mild/moderate/severe, guiding treatment intensity and follow-up frequency.

Mandatory comorbidity screening

  • Anxiety (GAD-7): present in up to 50% of adult ADHD — ADHD inattention is context-independent, anxiety-related inattention is tied to worry; both can coexist and both need treatment. If anxiety predominates, consider a non-stimulant first.
  • Depression (PHQ-9): ask whether inattention, disorganisation and impulsivity were clearly present in childhood, before the first depressive episode. If mood disorder is primary, treat it first and reassess ADHD once stable.
  • Bipolar disorder (MDQ): ADHD plus anxiety carries a high risk of undiagnosed bipolar disorder, and stimulants can precipitate or worsen mania. Red flags: distinct episodes of elevated mood, grandiosity, markedly reduced need for sleep, risky behaviour — if suspected, psychiatry review before any stimulant.
  • Substance use disorder (AUDIT + DAST-10 + urine drug screen): roughly double the risk in adult ADHD; active cannabis use mimics core ADHD symptoms for weeks after stopping. If SUD is active, address it first; if in stable remission, stimulant prescribing may be appropriate with specialist oversight.

Safety

  • Don't start a stimulant while bipolar disorder is suspected but unscreened — it can precipitate or worsen a manic episode.
  • Don't assume mood or anxiety symptoms are secondary to ADHD without checking the timeline — treat the primary condition first if it predates ADHD-like symptoms.
  • Don't proceed with stimulant prescribing in active, unstable substance use disorder.

Red flags / refer

  • Bipolar red flags present → psychiatry referral before any stimulant is considered.
  • Diagnostic uncertainty after Step 4 (rule-out), or overlapping autism/trauma features → specialist co-assessment.
  • Active SUD with suspected ADHD → specialist oversight for both, not GP-led initiation.

MH-01C v1.0 · Reviewed Jun 2026 · Review Jun 2027

For health-professional use. Framework: AADPA Clinical Practice Guideline, DSM-5-TR. Diagnosis is specialist-led, not a general-practice task. Companion sheets: MH-01A Recognition; MH-01B Screening & Referral; MH-01D Autism, Learning Disabilities & Workup.