Attention Deficit Hyperactivity Disorder (ADHD)
General Psychiatry Article Disclaimer
- DSM-5 criteria or ICD-11 diagnostic requirements are used to structure the Clinical Features and Diagnosis section. The classification system used is selected according to its clarity and suitability for non-specialist learning.
- The criteria are summarised and simplified rather than reproduced in full, while preserving their original diagnostic meaning.
- Where appropriate, a student-friendly pattern-recognition summary is provided to highlight the most clinically and exam-relevant features.
Exam tip (re-psychiatry questions)
- Do not attempt to memorise every DSM-5 or ICD-11 criterion word-for-word. However, it is important to read through the criteria and become familiar with the key symptom clusters, duration thresholds, exclusions, and distinguishing features highlighted in this article.
- Exam questions may not provide every feature required to meet the full diagnostic criteria. Familiarity with the criteria can help one recognise the most likely diagnosis, exclude important alternatives, and narrow the differential diagnosis.
Causes and Risk Factors
ADHD is a multifactorial condition arising from a combination of genetic and environmental factors [Ref]
Possible factors include: [Ref]
- Polygenic contribution (ADHD is rarely caused by a single-gene mutation or chromosomal abnormalities)
- Pregnancy and birth-related factors
- Prematurity
- Very low birth weight
- Maternal pre-eclampsia / hypertension
- Maternal obesity
- Maternal thyroid disorders
- Multiple prior miscarriages
- Prenatal or childhood exposure to environmental toxins, such as
- Organophosphate pesticides
- Lead
- Phthalate metabolites
- Maternal use of sodium valproate and paracetamol during pregnancy
- Psychosocial and extreme adversity (e.g. severe early deprivation, physical neglect, sexual abuse, low family income, out-of-home care, and familial exposure to severe substance abuse or criminality)
Associated Conditions / Comorbidities
ADHD is associated with the following: [Ref]
| Category | Specific conditions / comorbidities |
|---|---|
| Psychiatric and neurodevelopmental | ADHD often co-exists with the following:
|
| Substance use disorder |
|
| Metabolic and endocrine |
|
| Respiratory, immune and autoimmune |
|
| Neurological and sleep |
|
Clinical Features and Diagnosis
High-yield pattern recognition for ADHD:
ADHD may present from either or both of the following 2 core symptom domains:
- Inattention, classic features include:
- Frequent careless mistakes or poor attention to detail
- Appearing not to listen when spoken to
- Starting but failing to complete tasks
- Frequently losing essential items
- Being easily distracted
- Forgetfulness in daily activities
- Hyperactivity-impulsivity, classic features include:
- Hyperactivity
- Difficulty engaging in activities quietly
- Restlessness or excessive activity (e.g. difficulty remaining seated, excessive running, fidgeting or squirming)
- Appearing constantly active or “driven by a motor”
- Excessive talking
- Impulsivity
- Blurting out answers
- Difficulty waiting their turn
- Interrupting or intruding on others
- Hyperactivity
The symptoms above must also meet ALL of the following criteria:
- Persisted for at least 6 months
- Several symptoms should have been present before 12 y/o
- Symptoms occur in at least 2 different settings (e.g. home, school, work)
- Impacts social, educational, or occupational functioning
- Not be better explained by another mental disorder
According to the DSM-5 criteria, ADHD can be clinically diagnosed when ALL the following criteria are met: [Ref]
| Diagnostic criteria | Criteria description |
|---|---|
| Persistent ADHD symptoms | One or both of the following 2 symptom domains must be met
For either symptom domain, there should be at least 6 out of 9 symptoms that:
For those who are ≥17 y/o, only 5 symptoms are required Symptom domain 1: inattention
Symptom domain 2: hyperactivity-impulsivity
|
| Symptoms during childhood | Several inattentive or hyperactive–impulsive symptoms must have been present <12 y/o |
| Symptoms in multiple settings | Several symptoms must be present in at least 2 settings, such as:
|
| Functional impairment | Symptoms must:
|
| Exclusion criteria | The symptoms must:
|
Complications and Prognosis
Complications include: [Ref]
- Quality of life and social impairment
- Educational underachievement, lower employment rates, reduced earnings
- Higher risk of accidental injuries (e.g. vehicle crashes, head trauma, burns)
- Significantly higher risk of suicidal ideation, attempts and completed suicide
- Higher risk of criminal convictions and victimisation (making false police confessions and being a victim of violent or sexual crimes)
- Higher risk of impulsive behaviours (e.g. gambling, reckless spending), substance misuse
- Higher risk of teenage pregnancy
- Higher risk of developing dementia in adulthood
Management
<5 y/o
If a child or young person presents in primary care with suggestive ADHD that is adversely impacting their development or family life, consider:
- Watchful waiting for up to 10 weeks
- Offer referral to group-based, ADHD-focused support, which does not require a formal diagnosis to begin
If the symptoms persist and continue to cause at least moderate impairment after this 10-week period, refer to secondary care (e.g. child psychiatrist, paediatrician, or specialist ADHD CAMHS) for a full assessment
1st line management for diagnosed ADHD: conservative management
- Environmental modifications, such as
- Changing seating arrangement in class to minimise distractions
- Adjusting lighting and noise levels (e.g. using headphones)
- Optimising work or education routines to feature shorter periods of focus paired with movement breaks (e.g. using “I need a break” cards)
- Offer ADHD-focused group parent-training programme to the parents or carers
Do not routinely offer pharmacological treatment for ADHD to children who are <5 y/o
Young People
If a child or young person presents in primary care with suggestive ADHD that is adversely impacting their development or family life, consider:
- Watchful waiting for up to 10 weeks
- Offer referral to group-based, ADHD-focused support, which does not require a formal diagnosis to begin
If the symptoms persist and continue to cause at least moderate impairment after this 10-week period, refer to secondary care (e.g. child psychiatrist, paediatrician, or specialist ADHD CAMHS) for a full assessment
Management of formally diagnosed ADHD:
| Step / indication | Management |
|---|---|
| 1st line | Conservative management
Formal parent training should only be offered if the patient also has oppositional defiant disorder or conduct disorder in addition to ADHD |
| 2nd line (if there is significant impairment despite conservative management) | Pharmacological management
|
| 3rd line (if there is significant impairment despite pharmacological management) | Psychological intervention
CBT can be considered in those who benefit from medications but still experience significant impairment |
Adults
| Step / indication | Management |
|---|---|
| 1st line | Conservative management with environmental modifications, such as
|
| 2nd line (if there is significant impairment despite conservative management) | Pharmacological management
|
| 3rd line | Psychological intervention (structured supportive psychological intervention with regular follow-up +/- CBT)
Specifically indicated in ANY of the following:
|
Monitoring ADHD Medications
| Pre-treatment (baseline) assessment |
NICE noted that a routine ECG is NOT necessary |
| Ongoing monitoring |
NICE noted routine blood tests and ECGs are NOT recommended during ongoing treatment (unless there is a specific clinical indication) |