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The SNAPPER study is a stratified randomised controlled trial to evaluate the clinical and cost-effectiveness of Stimulant compared with Non-stimulant medication for adults with Attention deficit/hyperactivity disorder and a history of Psychosis or bipolar disorder.


The aim of SNAPPER is to evaluate the clinical and cost-effectiveness of stimulant (Lisdexamfetamine) compared with non-stimulant (Atomoxetine) medication for adults with Attention-Deficit/Hyperactivity Disorder (ADHD) and a history of either psychosis or bipolar disorder.

Update 28/03/2024: Total number of patients randomised: 43


SNAPPER is a pragmatic, observer-blind, national, multi-centre, stratified, 2-arm, parallel group randomised controlled trial with an internal pilot. Strata are defined according to a history of (1) Psychosis, or (2) Bioplar disorder.


Aim of the Study

The aim of the internal pilot is to assess recruitment as a proportion of the target for the entire trial. At 9 months, it is anticipated at 17% of the total recruitment will be met. 

The aim of the main study is to evaluate separately in adults with: (1) ADHD and a history of psychosis, and (2) ADHD and a history of bipolar whether stimulant (Lisdexamfetamine) vs. non-stimulant (Atomoxetine) medicated reduces ADHD symptom severity at 12 months.


Patients recruited from NHS secondary and tertiary community and inpatient mental health services across the UK.

Target Population

People aged 18 years and over. Existing or new diagnoses of ADHD and psychosis or bipolar disorder confirmed/ re-confirmed as part of study diagnostic screening assessments in people who are not currently (or within the last month) on medication for ADHD.


People consented to take part will be randomised to receive either:

  • Lisdexamfetamine (stimulant) initiated at 30mg once daily, and increased to a maximum of 70mg once daily for 12 months.


  • 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).

Measurement of outcomes

Primary outcome measure:

  • ADHD symptoms at 12 months post-randomisation, as measured by the Conners Adult ADHD Rating Scale-Observer (CAARS-O) total score.

Secondary outcome measures:

  • Longitudinal Interval Follow-up Evaluation (LIFE)
  • Positive and Negative Symptoms Scale (PANSS)
  • Difficulties in Emotion Regulation Scale (DERS-16)
  • Wender-Reimherr Adult Attention Definit Disorder Scale-Interview (WRAADS-Interview)
  • Adult ADHD QOL Measure (AADHD QOL)
  • Quality of life: EQ-5D-5L and ICEpop CAPability measure for Adults (ICECAP-A)
  • Functioning Assessment Short Test (FAST)
  • Drug Abuse Screening Test (DAST)
  • Alcohol Use Disorders Identification Test (AUDIT)
  • Medication Adherence Rating Scale (MARS)
  • Compliance self-report
  • Healthcare Resource Usage measured by the modified Client Service Recipient Inventory (CSRI).


More information...

Chief Investigator

Prof Steven Marwaha, Professor of Psychiatry. Institute for Mental Health, School of Psychology, University of Birmingham

Deputy Trials Management Team Leader

Shrushma Loi. Birmingham Clinical Trials Unit, University of Birmingham


National Institute of Health Research (HTA programme ref. NIHR 129817)


University of Birmingham


Central Bristol

EudraCT no.