Can losartan enhance the effects of cognitive behavioural therapy in the treatment of panic disorder?

INTERVENTION: Patients will be randomised to a group receiving losartan or placebo, with the participant and experimenter remaining blind to group allocation throughout the study. Blocked randomisation will be used where patients are allocated to sequential numbers while stratifying for gender and panic diagnosis (with agoraphobia/ without agoraphobia). Both groups will receive a single session of cognitive behavioural therapy (CBT), lasting for around 60 minutes, with the losartan group receiving a single dose of 50mg losartan 1 hour before CBT, and the placebo group receiving an identical‐looking placebo capsule. Effects of treatment on emotional processing will be measured on the day after treatment, clinical symptom severity will be measured one day, one month, and six months post‐treatment. CONDITION: Topic: Mental Health; Subtopic: Anxiety; Disease: Anxiety ; Mental and Behavioural Disorders ; Panic disorder PRIMARY OUTCOME: Symptom severity is measured using the clinician‐rated questionnaires Panic Disorder Severity Scale and Clinical Global Impression Scale at baseline, one month and six months post‐treatment, as well as the self‐report questionnaires State‐Trait Anxiety Inventory, Beck Depression Inventory, Panic Attack Scale, Agoraphobic Cognitions Questionnaire, Body Sensations Questionnaire, Mobility Inventory, Visual Analogue Scales during Stress at baseline, one day, one month and six months post‐treatment. SECONDARY OUTCOME: Emotion processing is measured using behavioural reaction time tasks at baseline and one day post treatment, as well as using a functional MRI one day post treatment. INCLUSION CRITERIA: 1. Participant is willing and able to give informed consent for participation in the study and to comply with all study requirements 2. Aged 18 years or above 3. Diagnosed with DSM­IV panic disorder 4. At least moderate avoidance of agoraphobic situations *Participants with MRI contraindications (e.g. pacemaker, metal implant, left‐­handedness) can be included in the study but will not undergo the MRI scan study component.