Depression and anxiety following a traumatic brain injury

Abstract

Traumatic brain injuries (TBI) are one of the leading global causes of death and disability, creating a substantial public health and socio-economic burden. The personal consequences of a TBI can also be extensive, commonly encompassing functional, cognitive and psychological problems. These impairments can, in turn, affect relationships, employment status, leisure activities and independence. The present thesis focuses on two of the most common psychological outcomes following TBI: depression and anxiety. Both undermine an individual’s quality of life, although their impact is not yet fully understood. The prevalence of depression and anxiety varies widely in the existing literature, but our understanding of what might be contributing to this variability is limited. This makes it difficult to identify who is most at risk of developing depression and/or anxiety following a TBI and when they are most susceptible. Crucially, this constrains our capacity to understand the trajectory of psychological problems after a TBI which, in turn, hampers clinicians’ ability to identify and implement targeted interventions for those who are most in need. The variability in rates likely reflects differences in how these problems are investigated, with data relating to the incidence, characteristics, risk factors and outcomes of TBIs collected in both epidemiological and clinical contexts. Adding to the problem is the fact that depression and anxiety are frequently measured using a variety of assessment methods and, moreover, there are often differences between the samples that are being examined, with studies evaluating individuals who have a variety of injury, and pre- and post-morbid characteristics. Thus, four studies were designed in order to examine these issues and comprehensively investigate whether, and to what extent, different methodologies and sample characteristics influence depression and anxiety after a TBI. The first study (Chapter 3) assessed the prevalence of clinical diagnoses of major depressive disorder (MDD)/dysthymia and self-reported ‘cases’ of clinically significant levels of depression following adult TBI. Data from 99 studies were meta-analysed. Overall, depression was found to be very common after a TBI, with 27% of people diagnosed with MDD/ dysthymia and 38% reporting clinically significant levels of depression. Next, Chapter 4 built on these findings by comparing levels of self-reported depression in people with and without a TBI who were living in the general community. The sample was recruited as part of a large, longitudinal study - the Personality and Total Health (PATH) Through Life project - which measured the health and well-being of young (20-24 years), middle-aged (40-44) and older adults (60-64), on three occasions (waves), four years apart. Across the total sample, clinically significant levels of depression were more prevalent in those who had sustained a TBI, regardless of the length of time that had elapsed since their injury. The next study (Chapter 5) focussed on anxiety, with data from 41 studies meta-analysed in order to examine the prevalence of generalized anxiety disorder (GAD) and self-reported ‘cases’ of clinically significant anxiety. Anxiety was also found to be common after TBI, with 11% of people formally diagnosed with GAD and 37% reporting clinically significant levels of anxiety on self-report questionnaires. Lastly, data from the PATH study were analysed (Chapter 6) in order to compare the levels of self-reported anxiety in people with and without a TBI. In cross-sectional analyses, across the total sample, clinically significant levels of anxiety were more prevalent (at each wave) in people who had incurred a TBI, regardless of the time that had elapsed since the injury. Moreover, comorbid anxiety and depression in those with a TBI was common, reinforcing the need for clinicians to identify and treat both problems in order to minimise their cumulative burden. Importantly, this thesis highlights a broad range of variables that influence the prevalence of depression and anxiety and, thus, should be considered by researchers and clinicians alike.