The Implications of an age of onset distinction for the presentation and treatment of late-life generalised anxiety disorder

Abstract

This thesis is an investigation of the implications of an age of onset distinction for the presentation and treatment of late-life generalised anxiety disorder (GAD). The main aim was to provide empirical evidence of a bimodal distribution of age at onset of GAD and a method for determining an appropriate cut-off to distinguish these two subgroups (Study One). The subsequent investigations included in Study One aimed to investigate differences in the aetiology and phenomenology of early-onset (EO) and late-onset (LO) GAD. In addition, the relationship between the experience of negative life events and age at onset of GAD was examined. Finally, Study Two aimed to investigate the implications of an age at onset distinction for the treatment of late-life GAD Study One included 76 older adults aged 55-84 years meeting diagnostic criteria for a current DSM-IV anxiety disorder, of which GAD was the most commonly diagnosed (96%). The results confirmed a bimodal distribution for first lifetime onset of GAD and an age of 34.4 years was identified as the cut-off point to distinguish between participants classified as having EO (n= 24) or LO (n = 56) GAD. EO participants reported significantly greater benzodiazepine and health supplement use; a longer history of anxiety; a greater number of episodes of anxiety and/or depression; a greater family history of psychiatric illness; greater severity of the symptom 'restlessness and/or feeling keyed up;' greater time spent worrying; greater distress, and; greater interviewer-rated severity of GAD than LO participants. On the other hand, LO participants reported greater functional limitations, poorer perceptions of health, and greater frequency and severity of both health-related events and difficult financial circumstances preceding first onset of GAD than those with EO GAD. The results also showed that that LO GAD was associated with the experience and accumulation of greater levels of life stress than EO GAD. Forty-one treatment-seeking participants (EO = 18 and LO = 23) who took part in the initial clinical assessment (Study One) completed a 12-week cognitive-behavioural therapy (CBT) program for GAD (Study Two). Measures of anxiety, worry and depression were completed at five time-points: at pre-treatment(T0), following completion of relaxation training (T1), cognitive skills (T2) and behavioural skills (T3) modules of therapy, and six-months following treatment completion (T4). Participant-rated evaluations of symptom severity and treatment efficacy were completed from T1 through to T4. The results showed that treatment resulted in significant improvements on all outcome measures from pre- to post-treatment and that these gains were maintained at six-month follow-up. Age of onset was not found to have a significant effect on treatment outcome. With exception of the finding that LO participants reported significantly greater symptom severity than EO participants at T1, onset groups did not differ in patterns of change over the course of treatment. The theoretical and clinical implications of the results and the need for further development of the understanding of an onset distinction in the presentation and management of late-life GAD through future research are discussed. Show more