Getting under the skin: Does biology help predict chronicity of depression?

Risk factors of chronic course of anxiety and depressive disorders: a 3-year longitudinal study in the general population

BACKGROUND

Risk factors of a chronic course of anxiety and depressive disorders were previously studied using a limited definition of recovery, i.e. remission of the index disorder. However, frequently, other mental disorders are present at follow-up. Thus, the course of anxiety and depressive disorders was represented too rosy and the identified determinants may not apply when using a broader, more realistic definition. Additionally, physical health risk factors have often been ignored.

METHODS

Data were used from two waves of the Netherlands Mental Health Survey and Incidence Study-2 including 509 respondents with 12-month anxiety disorder (panic disorder, social phobia, agoraphobia or generalized anxiety disorder) or/and major depressive disorder at baseline. Chronic course was defined as (1) presence of index disorder; and (2) presence of any anxiety, mood or substance use disorder (overall course) during the subsequent three years. Regression models were built with sociodemographic, clinical, and lifestyle/physical health indicators. Predictive accuracy was evaluated with area under the curve (AUC).

RESULTS

Chronic course of the index disorder was present among 24.8% of cases, whereas 38.7% had a chronic overall course. The accuracy of prediction of chronic course of the index disorder was suboptimal (AUC = 0.68) compared to prediction of overall course (AUC = 0.75). The main risk factors were baseline number of mental disorders, neuroticism, childhood abuse, parental psychopathology and alcohol use. Lifestyle and physical health indicators were marginally relevant.

CONCLUSION

Transdiagnostic risk factors are important in predicting overall course of anxiety and depressive disorders but cannot accurately predict chronic course of the index disorder.

Clinical research challenges posed by difficult-to-treat depression

Approximately one-third of individuals in a major depressive episode will not achieve sustained remission despite multiple, well-delivered treatments. These patients experience prolonged suffering and disproportionately utilize mental and general health care resources. The recently proposed clinical heuristic of 'difficult-to-treat depression' (DTD) aims to broaden our understanding and focus attention on the identification, clinical management, treatment selection, and outcomes of such individuals. Clinical trial methodologies developed to detect short-term therapeutic effects in treatment-responsive populations may not be appropriate in DTD. This report reviews three essential challenges for clinical intervention research in DTD: (1) how to define and subtype this heterogeneous group of patients; (2) how, when, and by what methods to select, acquire, compile, and interpret clinically meaningful outcome metrics; and (3) how to choose among alternative clinical trial design options to promote causal inference and generalizability. The boundaries of DTD are uncertain, and an evidence-based taxonomy and reliable assessment tools are preconditions for clinical research and subtyping. Traditional outcome metrics in treatment-responsive depression may not apply to DTD, as they largely reflect the only short-term symptomatic change and do not incorporate durability of benefit, side effect burden, or sustained impact on quality of life or daily function. The trial methodology will also require modification as trials will likely be of longer duration to examine the sustained impact, raising complex issues regarding control group selection, blinding and its integrity, and concomitant treatments.

Stress gets into the belly: Early life stress and the gut microbiome

Research has established that stress "gets under the skin," impacting neuroendocrine and neuroimmune pathways to influence risk for physical and mental health outcomes. These effects can be particularly significant for early life stress (ELS), or adverse childhood experiences (ACEs). In this review, we explore whether stress gets "into the belly," that is, whether psychosocial stress affects the gut microbiome. We review animal and human research utilizing a variety of stress paradigms (acute laboratory stressors, chronic stress, stressful life events, perceived stress, ELS, in utero stress) and their impacts on the gut microbiota, with a particular focus on ELS. We also review data on dietary interventions to moderate impact of stress on the gut microbiome. Our review suggests strong evidence that acute laboratory stress, chronic stress, and ELS affect the gut microbiota in rodents, and growing evidence that perceived stress and ELS may impact the gut microbiota in humans. Emerging data also suggests, particularly in rodents, that dietary interventions such as omega-3 fatty acids and pre- and pro-biotics may buffer against the effects of stress on the gut microbiome, but more research is needed. In sum, growing evidence suggests that stress impacts not only the neuroendocrine and neuroimmune axes, but also the microbiota-gut-brain-axis, providing a pathway by which stress may get "into the belly" to influence health risk.