Around 40% of people with Parkinson's disease experience anxiety, depression or a combination of the two (Reference Brooks and DoderBrooks & Doder, 2001). These rates are much greater than those observed in the general population, although the reasons for this are unclear. Factors associated with distress in Parkinson's disease have included hallucinations, cognitive impairment, stage of illness and functional disability (Reference Tandberg, Larsen and AarslandTandberg et al, 1997). However, these disease-related factors only account for a modest proportion of the variance in distress; psychological factors appear equally, if not more important (Reference Gotham, Brown and MarsdenGotham et al, 1986; Reference Maccarthy and BrownMacCarthy & Brown, 1989). The ‘self-regulatory executive function model’ (Reference Wells and MatthewsWells & Matthews, 1994) identifies several inter-related but distinct components of cognition linked to the development and maintenance of emotional disorder. It proposes that people hold beliefs about their own thought processes and these guide their responses to distressing cognitive or body state intrusions (pain, images, etc.). The model emphasises the role of negative beliefs about thoughts (e.g. ‘worrying is harmful’) and positive beliefs about a necessity to engage in worry or ruminative styles of coping. A cluster of responses tied to these beliefs (self-focused attention, worry/ruminative processing, attentional bias) underlie a wide range of emotional disorders (Reference WellsWells, 2000). This study tested the hypothesis that metacognitive style is associated with distress in Parkinson's disease independent of previously identified disease factors.

METHOD

RESULTS

We recruited 52 participants and excluded 8 because of recent neurosurgery, a history of alcohol misuse, pre-existing learning disability, diagnoses of dementia with Lewy bodies and bipolar disorder, and incomplete questionnaires (3).

The mean age of the remaining 44 (33 males) participants was 68.52 years (s.d.=9.61, range 25-81) and mean duration of illness was 7.19 years (s.d.=5.53, range 6 months to 23 years). The five stages of illness were represented: I (2, 5%), II (6, 14%), III (15, 34%), IV (13, 30%) and V (8, 18%); 17 (39%) and 19 (43%) of participants reached ‘possible caseness’ on the HAD for depression and anxiety, respectively. All except one were receiving anti-parkinsonian medication and six were receiving antidepressants.

DISCUSSION

These findings confirm the hypothesis that a more maladaptive metacognitive style is associated with heightened distress in Parkinson's disease. More specifically, people who held stronger negative beliefs about worry, focusing on its uncontrollability and danger, were more likely to report elevated levels of distress. This is in keeping with previous studies investigating such beliefs in anxiety disorders (Reference WellsWells, 2000) and challenges the notion that distress in Parkinson's disease is primarily a consequence of pathophysiology.

Two methodological limitations should be highlighted. The sample was recruited as part of another study investigating visual hallucinations in Parkinson's disease and was drawn from both community self-help groups and out-patient populations. This may have led to a bias towards recruiting people with hallucinations or less severe disease. Although some bias towards male participation was evident, the age, disease severity, duration of illness, and rates of anxiety, depression and hallucinations were comparable with those reported elsewhere (Reference Gotham, Brown and MarsdenGotham et al, 1986; Reference Di Rocco, Molinari, Kollmeier, Battistin, Scarloto, Caraceni and RuggieriDi Rocco et al, 1996).

Like previous studies, this research found increased anxiety and depression in the later stages of illness and when hallucinations were reported (Reference Tandberg, Larsen and AarslandTandberg et al, 1997; Reference Fenelon, Mahieux and HuonFenelon et al, 2000). Nevertheless, when these and other important disease factors were included in the multivariate analyses, metacognition remained a significant and independent predictor of distress. This is the first time that metacognitive beliefs have been investigated in chronic illness. The similarity between the distress observed in Parkinson's disease and other non-neurological movement disorders (e.g. arthritis; Reference Gotham, Brown and MarsdenGotham et al, 1986) suggests that these same results might be found in other chronic illnesses. Future research could investigate this possibility.

Worry is a normal phenomenon commonly reported in the general population and by people experiencing a range of chronic illnesses (Reference Wells and MorrisonWells & Morrison, 1994; Reference Fortune, Richards and MainFortune et al, 2000). Metacognitive beliefs may transform the meaning of mental events such that worry is itself appraised as uncontrollable and harmful. In this situation, individuals are likely to worry about Parkinson's disease and worry about their worry, thereby amplifying distress. This explanation resembles cognitive conceptualisations of generalised anxiety disorder, for which specific cognitive-behavioural techniques have been devised (Reference WellsWells, 2000). Future research should investigate whether these same techniques might ameliorate distress in Parkinson's disease.