Illness cognitions refer to ‘individuals’ common-sense definition of health threats' (Leventhal et al., 1998, p. 719), and ‘the patient's perception and understanding of the disease and treatment’ (Leventhal et al., 1986, p. 176). Concepts used as synonyms are illness beliefs, illness perceptions, illness representations, illness schemata and lay beliefs about illness (Scharloo & Kaptein, 1997). An elaborate and formal definition is proposed by Lacroix (1991): ‘a distinct, meaningfully integrated cognitive structure that encompasses (1) a belief in the relatedness of a variety of physiological and psychological functions, which may or may not be objectively accurate; (2) a cluster of sensations, symptoms, emotions and physical limitations in keeping with that belief; (3) a naïve theory about the mechanisms that underlie the relatedness of the elements identified in (2); and (4) implicit or explicit prescriptions for corrective action’ (p. 197).
Social cognitive models propose that individuals develop their own mental representation of health threats and these cognitions guide coping responses and set the criteria for appraisal of outcomes. Individuals' responses to stimuli, such as physical symptoms and signs, are partly determined by individuals' cognitions (or ideas, thoughts, views) about those stimuli. Social cognition models aim to shed light on these cognitions in order to describe, understand and change responses of individuals to these stimuli (Conner & Norman, 1996). The concept of ‘lay illness models’ is related to the illness cognition concept (Schober & Lacroix, 1991) (see ‘Lay beliefs of health and illness’).