Diagnosis has a degree of subjectivity, with symptoms expected to appear “often”. There should be a full clinical and psychosocial assessment of the person, a full developmental and psychiatric history and observer reports and assessment of the person’s mental state. This can include observations, for example from school, when there is doubt about symptoms.¹

NICE advises that the diagnostic criteria of the International Classification of Diseases 11th Revision (ICD-11) and the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, (DSM-5) be followed.

DSM-5 lists symptoms of inattention and hyperactivity-impulsivity and requires at least 6 symptoms in each category to have persisted for at least 6 months. A symptom needs to occur “often” to contribute to diagnosis.²

To consider where the boundary with normality is crossed, the ICD-11 acknowledges that inattention, hyperactivity and impulsivity symptoms are present in many people, especially during certain developmental periods. ADHD diagnosis therefore “requires that these symptoms be persistent across time, pervasive across situations, significantly out of keeping with developmental level, and have a direct negative impact on academic, occupational, or social functioning.”³