Aims: Few studies have investigated the aetiology of chronic disabling fatigue in children. Our aim is to investigate whether chronic disabling fatigue in 13 year-old children in the ALSPAC cohort is predicted by a range of factors, including maternal psychopathology, childhood psychological problems, adverse life events, behavioural problems, exercise, obesity, and sleep patterns.

Hypotheses: Maternal and childhood psychological, environmental and lifestyle factors may be associated with chronic disabling fatigue at age 13-14 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 10 time points between pregnancy and child age 9-10 years; childhood psychological problems (derived from the 'Development and Well-Being Assessment' (DAWBA) questionnaire), upsetting events, and behavioural problems (from the 'Strengths and Difficulties Questionnaire' (SDQ)) occurring at age 7-9 years; sleep patterns at 8 timepoints; body mass index; diet (food frequency questionnaire and dietary diaries); and physical activity (questionnaire and accelerometer data).

Outcome variables: We have identified 117 & 53 ALSPAC 13 year-olds with disabling fatigue of >=3 and >=6 months duration, respectively, 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].

Confounding variables: family adversity.