A clinical trial to investigate how effective a stimulant medication is compared to a non-stimulant medication in patients who have been diagnosed with attention deficit hyperactivity disorder (ADHD) and also have a history of either psychosis or bipolar disorder

INTERVENTION: Patients will randomised to receive either Lisdexamfetamine (stimulant) initiated at 30mg once daily, and increased to a maximum of 70mg once daily for 12 months; OR Atomoxetine (non‐stimulant) initiated at 40mg daily, and increased to a maximum of 100mg daily for 12 months (if on Fluoxetine then starting dose should be halved e.g., 20mg if weight > 70kg). Randomisation will be provided by a secure online randomisation system at the Birmingham Clinical Trials Unit (BCTU) CONDITION: Attention‐Deficit/Hyperactivity Disorder (ADHD) and a history of either psychosis or bipolar disorder ; Mental and Behavioural Disorders PRIMARY OUTCOME: ADHD symptoms at 12 months measured using the Conners Adult ADHD Rating Scale‐Observer (CAARS‐O) total score SECONDARY OUTCOME: ; 1. Clinical (ADHD symptoms using CAARS‐O total score at 6 months, emergence of hypomania/mania symptoms, emergence of psychotic symptoms and depression over 12 months; emotional dysregulation at 6 and 12 months).; 2. Quality of life (QOL) (ADHD specific QOL for participants only using the Adult ADHD QOL (AADHD QOL); health‐related QOL and capability wellbeing for both the participant and supporter (close person) at 6 and 12 months) using the EQ‐5D‐5L and ICECAP‐A.; 3. Occupational and functional outcomes (occupational and daily functioning, employment, education at 6 and 12 months) using the Functioning Assessment Short Test (FAST).; 4. Substance misuse (problem drug use, problem drinking at 6 and 12 months).; 5. Adherence at 6 and 12 months (Medication Adherence Rating Scale (MARS) and self‐reported adherence at, 6, and 12 months; pill counting on prescription review).; 6. Process outcomes (all causes for discontinuation of treatment).; 7. Resource use (modified Client Service Receipt Inventory (CSRI) and use of acute services at 6 and 12 months).; 8. Concomitant medication use (type, dose and duration) at 6 and 12 months.; INCLUSION CRITERIA: 1. Diagnosis of ADHD according to the Diagnostic and Statistical Manual of Mental Disorders 5th edition (DSM‐5) based on the Diagnostic Interview for ADHD in Adults‐5 (DIVA‐5) 2. Psychosis (schizophrenia spectrum disorders) (Strata 1) OR Bipolar disorder (Strata 2) diagnosis according to the DSM‐5 based on the Mini International Neuropsychiatric Interview (MINI) 3. Stable and on suitable mood stabilisers or antipsychotics 4. Males and females aged 18 years and over 5. Not currently (or within the last month) on medication for ADHD 6. Able to give written informed consent