The investigators have developed self-help booklets specifically for adults with PH who are experiencing difficulties with depression. The self-help booklets are based on a type of psychological treatment called Cognitive Behavioural Therapy or CBT for short. * CBT looks at the way people think and what they do, and how this affects their mood. * It involves making changes to thoughts and behaviours. * CBT can help people develop more helpful ways of coping with depression. * CBT is one of the most effective therapies for depression, this means it works well. There are four booklets that participants will work though weekly in their own time and at home. The aim of this study is to test whether the self-help booklets are helpful in reducing depression in people with pulmonary hypertension. Those taking part will be asked to complete a series of questions asking about themselves including whether they are experiencing any difficulties such as depression and anxiety. They will then be allocated at random to one of two groups. Group one will receive the self-help booklets, called the intervention group. Group two, or the wait list group, will receive the intervention at a later date if it is found to be helpful. Having two groups is very important as it will allow us to see whether benefits associated with taking part in the project was because of the self-help booklets or something else. Participants in group one will also be contacted partway through the intervention to ask about their experiences of taking part. Both groups will be asked to complete a series of questionnaires four weeks later and then again in one month. Participants in group one will be contacted again to find out more about their experiences of the project.