Why are ADHD and bipolar disorder often misdiagnosed

PostedNovember 20, 2025

UpdatedNovember 21, 2025

ByMy Patient Advice

Author: Harriet Winslow, BSc | Reviewed by: Dr. Rebecca Fernandez, MBBS

ADHD and bipolar disorder share many overlapping symptoms, which often leads to confusion in diagnosis, especially in adults. According to NHS guidance and NICE clinical recommendations, both conditions can present with impulsivity, emotional instability, and fluctuating energy levels. However, their timelines, intensity, and underlying mechanisms differ significantly.

Symptom overlap and diagnostic confusion

Both ADHD and bipolar disorder involve mood shifts, restlessness, and poor impulse control, making it difficult to tell them apart in clinical settings. A PubMed review found that up to 20% of adults with either diagnosis was initially misclassified due to shared emotional dysregulation. The difference lies in duration and cause: ADHD mood changes are short-lived and situational, while bipolar mood episodes last days or weeks and feature clear manic or depressive phases. NICE notes that relying on surface-level symptoms, rather than timelines and developmental history, is a key source of diagnostic error.

Clinical guidance and differentiation

The NICE NG87 ADHD guideline and NICE CG185 bipolar guideline recommend full developmental and collateral histories to separate lifelong ADHD traits from episodic mood patterns. ADHD is typically present from childhood and remains consistent, whereas bipolar disorder develops later and follows an episodic course. The Royal College of Psychiatrists also highlights that emotional intensity in ADHD is reactive and short-term, unlike the sustained mania or depression seen in bipolar presentations.

Neurobiological and behavioural differences

Neuroimaging and genetic studies show overlapping dopamine pathway involvement in both conditions, but ADHD primarily affects attention and executive control, while bipolar disorder involves mood regulation networks. According to BMJ Best Practice, recognising differences in symptom progression such as ADHD’s continuous pattern versus bipolar’s cyclical episodes is essential to accurate diagnosis. Misinterpreting ADHD hyperactivity as hypomania or bipolar irritability as ADHD impulsivity remains a common pitfall in adult mental health care.

Improving diagnostic accuracy

NICE and NHS England emphasise multidisciplinary evaluation, combining input from GPs, psychiatrists, and psychologists, alongside structured diagnostic tools. Collateral information from family or educational history helps confirm ADHD onset before age 12, while screening for manic or hypomanic episodes ensures bipolar features are not overlooked. In the UK, private assessment services such as ADHD Certify can also support complex diagnostic clarification in adults where both conditions are suspected.

Key takeaway

ADHD and bipolar disorder frequently overlap in how they appear but differ in duration, pattern, and neurobiology. According to NICE and NHS, accurate diagnosis depends on detailed developmental history, structured assessment, and multidisciplinary collaboration. With careful evaluation, adults can receive appropriate treatment for both conditions, improving long-term stability, focus, and emotional wellbeing.

Harriet Winslow, BSc

Author

Harriet Winslow is a clinical psychologist with a Bachelor’s in Clinical Psychology and extensive experience in behaviour therapy and developmental disorders. She has worked with children and adolescents with ADHD, autism spectrum disorder (ASD), learning disabilities, and behavioural challenges, providing individual and group therapy using evidence-based approaches such as CBT and DBT. Dr. Winslow has developed and implemented personalised treatment plans, conducted formal and informal assessments, and delivered crisis intervention for clients in need of urgent mental health care. Her expertise spans assessment, treatment planning, and behavioural intervention for both neurodevelopmental and mental health conditions.

All qualifications and professional experience stated above are authentic and verified by our editorial team. However, pseudonym and image likeness are used to protect the author's privacy.

Dr. Rebecca Fernandez, MBBS

Reviewer

Dr. Rebecca Fernandez is a UK-trained physician with an MBBS and experience in general surgery, cardiology, internal medicine, gynecology, intensive care, and emergency medicine. She has managed critically ill patients, stabilised acute trauma cases, and provided comprehensive inpatient and outpatient care. In psychiatry, Dr. Fernandez has worked with psychotic, mood, anxiety, and substance use disorders, applying evidence-based approaches such as CBT, ACT, and mindfulness-based therapies. Her skills span patient assessment, treatment planning, and the integration of digital health solutions to support mental well-being.

All qualifications and professional experience stated above are authentic and verified by our editorial team. However, pseudonym and image likeness are used to protect the reviewer's privacy.