Aims: Few studies have investigated the aetiology of chronic disabling fatigue in children. Our aim is to investigate whether chronic disabling fatigue in 16 year-old children in the ALSPAC cohort is predicted by a range of factors, including maternal psychopathology, childhood psychological problems, exercise, and obesity.

Hypotheses: Maternal and childhood psychological, environmental and lifestyle factors may be associated with chronic disabling fatigue at age 16-17 years.

Exposure variables: episodes of maternal anxiety (Crown-Crisp Experiential Index anxiety subscale score greater than 8) and depression (Edinburgh Depression Scale score greater than 12) occurring at up to multiple time points since pregnancy; childhood psychological problems (derived from the 'Development and Well-Being Assessment' (DAWBA) questionnaire) at age 15 years; body mass index; and physical activity (questionnaire and accelerometer data); chronic fatigue at at 13-14 years (defined as fatigue that had prevented school attendance or participation in activities and that was not due to sport, possible sleep apnoea or probable depression [Crawley E, Hughes R, Northstone K, Tilling K, Emond A, Sterne JA. Pediatrics. 2012;130(1):e71-9]).

Outcome variables: We will identify ALSPAC 16 year-olds with high levels of fatigue using an appropriate threshold on the Chalder Fatigue Scale. This questionnaire was included in TF3. The threshold will be defined by looking at Chalder Fatigue scores in children diagnosed with CFS/ME according to National Insititute for Health & Clinical Excellence (NICE) diagnostic criteria using data from a cohort of paediatric patients which is maintained in the Centre for Child & Adolescent Health.

Confounding variables: family adversity