Generalised Anxiety Disorder and Depression: Contemporary Treatment Approaches

Anxiety and depression form a large group of interrelated, overlapping psychiatric disorders whose precise taxonomy and terminology can at first be confusing. In this supplement, we will mainly discuss generalised anxiety disorder (GAD), major depressive disorder (MDD) and anxious depression. Figure 1 shows how GAD and MDD fit into the overall disease classifications of anxiety and depressive disorders, as defined in the Diagnostic and Statistical Manual of Mental Disorders (Fifth Edition; commonly referred to as DSM-5) [1].

Current diagnostic criteria for GAD and MDD are shown in Table 1. GAD and MDD are prevalent, debilitating illnesses that frequently coexist [2]. In severe cases, GAD may be associated with disabling symptoms, social and occupational impairment, an increased risk of suicidality, and reportedly low rates of treatment response [3, 4]. In patients with a major depressive episode, coexisting symptoms of anxiety (or ‘anxious depression’) increase the severity of depression, worsen functional impairment, reduce quality of life, and add to the economic burden [5]. Although there are now effective treatments for GAD, many patients do not respond, are unable to tolerate them, or experience discontinuation symptoms when treatment is stopped [6]. Additionally, there are effective treatments for anxious depression, but these have been less thoroughly researched [7].

At a population level, the burden of human disease (or ‘health loss’) can be measured in terms of disability adjusted life-years (DALYs). The total number of DALYs for a given population has two components: premature death, which is quantified as the number of years of life lost due to disease or injury; and morbidity, which is quantified as the number of years lived with disability (YLD) [8]. YLD is particularly relevant to mental illnesses such as GAD and MDD. Data from the Global Burden of Disease Study 2019 show that the societal impact of anxiety and depression is extremely high, in both absolute and relative terms. Both disorders are associated with very significant global health losses, predominantly due to high numbers of associated YLDs (Table 2) [9, 10]. Importantly, these losses are seen globally, occurring in low- and middle-income countries, as well as in wealthier nations [10]. Moreover, both disorders are prominent contributors to global DALYs among adults of working age [9], a finding with considerable socioeconomic implications. In the USA, MDD was the second-largest contributor to YLDs in 2010, while anxiety disorders together were the fifth largest [11]. The percentage of global YLDs attributable to depression and anxiety remained relatively stable between 1990 and 2019 [10]; this is despite considerable ongoing research, the availability of numerous effective pharmacotherapies, and the growth and diversification of psychological treatment options.

Traditionally, clinical psychiatry has emphasised treatment rather than prevention and focused on manifestations rather than causes. Moving forward, should psychiatry shift its focus to identifying at-risk individuals and intervening earlier, with the objectives of preventing illness or reducing its severity and duration? Screening for at-risk individuals or possible causes of GAD (e.g. excessive perceived threat), as well as symptoms and signs of GAD in patients with or without MDD, could form part of such a strategy, given that GAD often has earlier onset than MDD and may increase vulnerability to developing MDD. Additionally, there is growing interest and research into the neurobiological mechanisms of GAD, which may ultimately allow for the development of targeted treatments. Evolutionary medicine may also offer clues as to how we approach GAD and MDD in the future, e.g. by viewing anxiety and depression as adaptive responses to particular circumstances, which may at times be excessive, analogous to the current understanding of allergies based on adaptive immune responses, which at times are disproportionate.

For now, we have effective pharmacotherapies both for GAD and for anxiety associated with MDD. In both conditions, treatment has the potential to decrease or relieve symptoms, improve or restore functioning, and increase health-related quality of life. From a public health point of view, the cost-effectiveness of treatments for GAD and MDD is worth emphasising. In this supplement, we review the evidence base that supports treatments for GAD in 2021—both pharmacological and non-pharmacological—with a particular focus on recent meta-analyses and emerging treatments. We will also explore how our understanding of the relationship between anxiety and depression has evolved, and summarise current best practice in the management of anxious depression.