I am doing an RCT in New Zealand and one of the before and after measures I want is family relationships. The intervention will last 6-8 weeks, so I am looking for an instrument that can pick up changes within this timeframe. It would be good but not essential if the questionnaire also asked about the quality of life. The intervention will involve NZ adolescents and one adult family member, so having both perspectives would be ideal.
Is there a validated questionnaire that's suitable?