Affiliations: School of Psychology, University of Nottingham,
Nottingham, NG7 2RD, UK. Tel.: +44 115 9 515327; Fax: +44 115 9 515324;
E-mail: [email protected]; [email protected]
Abstract: Non-specific illness includes a wide variety of symptoms:
behavioural (e.g., reduced food and water intake), cognitive (e.g., memory and
concentration problems) and physiological (e.g., fever). This paper reviews
evidence suggesting that such symptoms can be explained more parsimoniously as
a single symptom cluster than as a set of separate illnesses such as Gulf War
Syndrome (GWS) and chronic fatigue syndrome (CFS). This superordinate syndrome
could have its biological basis in the activity of pro-inflammatory cytokines
(in particular interleukin-1: IL-1), that give rise to what has become known as
the 'sickness response'. It is further argued that the persistence of
non-specific illness in chronic conditions like GWS may be (in part)
attributable to a bio-associative mechanism (Ferguson and Cassaday, 1999). In
the case of GWS, physiological challenges could have produced a non-specific
sickness response that became associated with smells (e.g., petrol),
coincidentally experienced in the Persian Gulf. On returning to the home
environment, these same smells would act as associative triggers for the
maintenance of (conditioned) sickness responses. Such associative mechanisms
could be mediated through the hypothalamus and limbic system via vagal nerve
innervation and would provide an explanation for the persistence of a set of
symptoms (e.g., fever) that should normally be short lived and self-limiting.
We also present evidence that the pattern of symptoms produced by the
pro-inflammatory cytokines reflects a shift in immune system functioning
towards a (T-helper-1) Th1 profile. This position contrasts with other
immunological accounts of GWS that suggest that the immune system demonstrates
a shift to a Th2 (allergy) profile. Evidence pertaining to these two
contrasting positions is reviewed.
Keywords: cytokines, interleukin-1, stress, Gulf War Syndrome, Pavlovian conditioning, neurodegeneration
