• T Theorell, V Blomkvist, G Lindh, and B Evengård.
• National Institute for Psychosocial Factors and Health, Stockholm, Sweden.
• Psychosom Med. 1999 May 1;61(3):304-10.

ObjectiveThe purpose of this study was to describe the sequence of psychosocial events and infections preceding the onset of chronic fatigue syndrome (CFS). This information was related to the temporal development of crucial symptoms in relation to the onset of, namely, fatigue, sadness, irritability, pain, and feeling of fever.MethodsA personal interview was conducted in 46 patients (mean age, 39.5 years; SD, 9 years) who fulfilled international CFS criteria. These patients were matched with regard to age and gender to 46 carefully matched control subjects. Twenty-three percent of the study subjects were men, and 77% were women. The patient at first identified the month that coincided with the onset of CFS. Similarly, each control subject was asked to identify a "very difficult period" within approximately the same period as the patient with whom the control subject was matched. A list of 14 different life events was perused. Participants were asked to identify for each month whether each of the listed events had occurred. Furthermore, they were asked to rate the importance of the events they had experienced. In addition, for each of the cardinal symptoms (fatigue, sadness, irritability, pain, and feeling of fever) and for each month, the subjects were asked to rate, on a visual analogue scale, the symptom intensity. Also, the number of infections was noted.ResultsA statistically significant group difference in fatigue intensity existed during the period 4 to 10 months before the onset of CFS. During the 3 months preceding the diagnosis for the CFS patients or the peak of the crisis for the control group, there was a dramatic rise in fatigue in both groups. The CFS group reached a much higher fatigue level, which leveled off somewhat during the first year of follow-up but still remained very high in comparison with the control group, which reached precrisis levels 4 months after the peak. Similar patterns were observed for fever and pain. With regard to sadness and irritability, no group difference was observed during the period preceding the crisis. In the patient group, the level stayed high throughout the whole first year of follow-up, whereas a slow return started in the control group; precrisis levels were reached after 1 year in this group. The prevalence ratio (CFS patients/control subjects) for negative events was around 1.0 for the periods 4 to 12 months preceding CFS but 1.9 during the quarter year preceding the onset. For infections, the prevalence ratio increased successively during the four quarters preceding CFS (from 1.4 to 2.3).ConclusionsAccording to the retrospective self-reports, there were differences between the groups in fatigue, pain, and feeling of fever during the months preceding the crisis. With regard to depressive and irritable feelings, no preillness differences were reported between the groups. There was a reported excess prevalence of both infections and negative life events during the quarter year preceding the onset of CFS or crisis. Potential sources of error are discussed. These findings must be replicated in longitudinal studies.

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