Adult patients with ADHD commonly report an improvement in behavioural symptoms when using cannabis with some reporting a preference towards cannabis over their ADHD stimulant medication. The EMA-C study aims to investigate the effects of a cannabis based medication, Sativex Oromucosal Spray on behaviour and cognition in adults with ADHD.

This will be carried out by conducting a placebo controlled trial. 30 adults with ADHD will take Sativex or a dummy medication (a placebo) every day for 6 weeks. There is a 50% chance of receiving the Sativex or Placebo. Measures of behaviour and cognition will be taken before and after 6 weeks of treatment. We hypothesise that treatment with Sativex will result in improvements in behaviour and cognition above that of the placebo group.

Inclusion Criteria:

• The study is open for both men and women aged 18-55 who meet DSM 5 criteria for ADHD (N= 30). Subjects will be either unmedicated or medicated with stimulant medication only and be willing to come of this medication for 1 week before and for the duration of the study. To ensure that this does not disadvantage patients we will only include those on stimulant medication who do not take medication on a regular basis and where short periods of medication are not thought by both the patient and psychiatrist to represent a clinical problem in the overall control of the symptoms and impairments. For example, by including patients who are considering a "stimulant drug holiday", which is a common clinical procedure in ADHD. Subjects must not use other prescription and non-prescription medication or recreational drugs during the study.

Exclusion Criteria:

• Exclusion criteria will include autism spectrum disorders and other psychiatric disorders including recurrent major depression, bipolar I disorder, any psychotic disorder and obsessive compulsive disorder and learning difficulties defined as an IQ < 70. Neurological problems and known or suspected history of a drug or alcohol dependence disorder. Subjects who are using or have used cannabis or cannabis based medications in the 30 day period prior to study entry. Concurrent history of renal, hepatic, cardiovascular or convulsive disorders. Females who are pregnant or breastfeeding. Female subjects of child bearing potential and male subjects whose partner is of child bearing potential, unless willing to ensure that they or their partner use two effective forms of contraception, for example, oral contraception, double barrier, intra-uterine device, during the study and for three months thereafter (Note: a male condom should not be used in conjunction with a female condom).