This project will introduce a self-help parent training programme for families on National Health Service (NHS) waiting lists for child mental health services. It will examine whether access to treatment can be increased by providing an intervention that requires fewer resources and by releasing clinician time for more serious cases. This intervention will be tested in a randomised, controlled trial in which 35 subjects will receive treatment immediately and 35 will receive treatment after waiting for 10 weeks. All families will also complete questionnaires before and after the 10 week study period in order to measure changes in child behaviour, parenting, and parental mental health. Cost-effectiveness of this programme will also be analysed. Intention-to-treat analyses will be conducted.

Inclusion Criteria:

• Families on waiting lists and child and adolescent mental health services clinics with children aged 2-5.
• Scores in the clinical range on a standardised measure of child behaviour problems.
• At least one parent in each family must be literate, fluent English speakers to participate because the self-administered intervention will primarily consist of written instructions and information in English.

Exclusion Criteria:

• Clients whose children score below a clinical cut-off score on a standardised measure of child behaviour problems. This is to ensure that participants are appropriate for an intervention aiming to reduce behaviour problems.
• Non-English speakers or those who are unable to read cannot be included because reading English is required to complete the self-administered intervention.
• Children or parents with severe disabilities and children with a developmental disorder (e.g., autism) will be excluded because the version of the parent training programme that will be implemented is not designed for families with these types of problems.
• Children who live with a temporary caregiver will be excluded because the intervention is designed for full-time parents and follow-up will be after one year.
• Children or parents who are currently receiving treatment for psychological problems will be excluded because outcomes may be influenced by interventions not affiliated with this project.