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Bipolar disorder and ADHD share a long list of surface features: distractibility, talking too much, restlessness, impulsive decisions, poor sleep and irritability. On a symptom checklist they can look almost identical. Over time they look very different, and that difference is what an adult assessment has to establish.
This guide sets out how to separate the two, what to do when both are present, and what the report needs to say. It is the companion to our guide on separating ADHD from EUPD, and the same principle applies: the shape of the symptoms over time matters more than the symptoms themselves.
ADHD is a trait. Bipolar disorder is a series of episodes. Most of the differential follows from that.
Several DSM-5-TR criteria for a manic or hypomanic episode describe behaviour that many adults with ADHD show every day: distractibility, being more talkative than usual, racing thoughts, increased activity and risky decisions. A patient who ticks those boxes on a questionnaire has not told you which condition they have. They have told you that one of them needs to be ruled in or out.
The confusion runs both ways. Someone with undiagnosed ADHD can be labelled with a mood disorder because of chronic irritability and chaotic sleep. Someone with bipolar II disorder can present between episodes with poor concentration, screen positive for ADHD and be started on a stimulant without anyone asking about past hypomania.
Ask whether the symptoms are a change from the person’s usual self, or the person’s usual self.
In ADHD, the difficulties are trait-like. DSM-5-TR requires several symptoms to have been present before the age of 12, and NICE guideline NG87 (1.3.1) recommends that diagnosis is based on a full developmental and psychiatric history, among other things. The patient, and the people who know them, usually describe someone who has always been like this.
Bipolar disorder is episodic. DSM-5-TR requires a distinct period of abnormally elevated, expansive or irritable mood with increased energy: at least one week for mania (or any duration if hospitalisation is needed) and at least four consecutive days for hypomania. The person, or their family, can usually point to a time when they were noticeably not themselves, and a time when they returned to baseline.
The European consensus statement on adult ADHD (Kooij and colleagues, 2019) puts it in similar terms: emotional dysregulation in ADHD is different from episodic symptoms. It describes ADHD mood changes as short-lived and exaggerated, within an essentially normal range of moods, compared with the more severe extremes of depression and elation seen in bipolar disorder.
The distinction is harder with rapid cycling, mixed features, cyclothymia or persistent symptoms between episodes, where mood instability can look more continuous. These are the cases where an informant and a long timeline matter most.
None of these is decisive on its own, but each should prompt a closer look at mood history:
The firmest evidence in this differential comes from a timeline. A few practical approaches help:
Screening questionnaires can prompt questions but cannot settle this differential. NG87 1.3.2 states that an ADHD diagnosis should not be made solely on the basis of rating scale or observational data. A high score on an ADHD screen in someone with an unrecognised mood disorder is a reason for a fuller assessment, as our guide to what a positive ADHD screen means explains.
ADHD and bipolar disorder often occur together. In a 2021 meta-analysis of 71 studies, Schiweck and colleagues estimated that around 8% of adults with ADHD also had bipolar disorder, and around 17% of adults with bipolar disorder also had ADHD.
DSM-5-TR Criterion E requires that ADHD symptoms are not better explained by another mental disorder, and our guide to documenting Criterion E covers this in detail. The test is whether the ADHD symptoms are accounted for by the mood episodes. If inattention and disorganisation are also present when mood is stable, and were present in childhood, both diagnoses can stand.
Getting this right affects safety. NG87 1.7.19 advises that if someone with ADHD has an acute psychotic or manic episode, any ADHD medication should be stopped, and restarting or starting new ADHD medication considered after the episode has resolved, taking into account the individual risks and benefits. NG87 1.7.4 also recommends a review of coexisting mental health conditions before medication is started.
The evidence on stimulants in people with bipolar disorder is limited and largely observational. In a Swedish registry study of adults with bipolar disorder (Viktorin and colleagues, 2017), people taking methylphenidate without a mood stabiliser had a markedly higher rate of mania in the first three months of treatment. Among those also taking a mood stabiliser, there was no increase, and the rate was if anything lower. The authors advised assessing for bipolar disorder before starting methylphenidate without a mood stabiliser.
The 2019 European consensus suggests that, where both conditions are present, the bipolar disorder is usually treated first, and that stimulants can then be used for ADHD provided the person is also taking a mood stabiliser. The prescriber should record this sequence and monitor mood at each titration review. Our adult ADHD titration protocol sets out what a titration plan should cover.
A report that addresses this differential openly is easier to defend and more useful to the next clinician. It should:
Our guide to writing the ADHD diagnostic report covers structure and wording in more detail.
No. Questionnaires can show that symptoms are present, but not whether they are lifelong or episodic. That depends on a detailed history, ideally with an informant.
Yes, and it is not rare. Both diagnoses can be made if ADHD symptoms began in childhood and are present when mood is stable.
Observational evidence suggests a higher risk of mania when methylphenidate is taken without a mood stabiliser by people with bipolar disorder. NICE advises stopping ADHD medication during an acute manic episode.
Differential diagnosis and comorbidity run through every adult assessment. Our ADHD Assessor Training course covers the diagnostic interview and the history that supports it, and the ADHD Prescribing and Management course covers treatment decisions when other conditions are present.
If you would like to see how an experienced assessor handles a complex history in a live assessment, the Observership Academy pairs you with a senior clinician for a remote placement.
The symptoms of ADHD and bipolar disorder overlap, but the course over time usually differs. A clear timeline, an informant and a careful sleep history resolve many cases. Where both conditions are present, saying so plainly, and setting out the treatment implications, is more useful than forcing a single answer.
