Depression sub-typing: unitary, binary or arbitrary?

A meta-analysis of cranial electrotherapy stimulation in the treatment of depression

BACKGROUND

Depression rates have reached historic highs, with 49% of Americans reporting unabating symptoms and signs of depression, representing a 12% increase compared to the same time in 2019. With depression as a moderating factor for suicide, the need for efficacious treatments for depression has never been more pronounced. Although the armamentarium of the psychiatrist seems impressive having multiple medications and psychotherapy options, with guidelines for combination and augmentation treatments; many patients do not improve or are not suitable candidates for the usual, customary and reasonable (UCR) depression treatments. The use of various forms of brain stimulation technology as a complementary or alternative treatment for depression is growing and is expected to be part of the armamentarium of most psychiatrists by 2030. One form of brain stimulation, available in a phone sized prescription device, is cranial electrical stimulation (CES) which has been used as a treatment for depression since the 1970s. We have conducted two meta-analyses of CES research for depression separating randomized controlled trials (N = 5) from non-randomized studies on interventions (N = 12). For the double-blind RCTs 100 μA was used for 1 hour per day as 100 μA is a subsensory level of current so identical sham treatment devices could be used.

METHODS

Our literature review followed Cooper's Taxonomy of Literature Reviews that is appropriate for the behavioral and physical sciences and the PRISMA reporting guidelines. The evaluation of strengths and limitations of the research studies included in this report adheres to recommended published guidelines in the Cochrane Handbook for Systematic Reviews of Interventions, and in the Handbook of Research Synthesis and Meta-Analysis. We used the Cohen's d effect size summary metric in all analyses. Homogeneity of effect sizes within the fixed and random effects models are reported. Meta-analyses were performed using the Compressive Meta-Analysis, version 3 program.

RESULTS

The 5 RCTs represent a combined N of 242 and the 12 NRSIs represent 16 data sets with a combined N of 1173 for total of 1415 subjects across 17 studies. There were male and female subjects, from adolescents to 60 years old. The average effect for the 5 RCTs was calculated as d = -0.69 (i.e., the mean depression level at posttest for the active group was -0.69 standard deviations lower than the mean depression level for the sham group), a medium effect. The additional 12 NRSI studies analyzed show a small effect of d = -0.43 in favor of the active treatment group.

CONCLUSION

We conclude that CES has a small to medium significant effect in symptoms of depression across moderate to severe patients in civilian, military, veterans, advanced cancer and pediatric populations.

Depression: discrete or continuous?

Elucidating the true structure of depression is necessary if we are to advance our understanding and treatment options. Central to the issue of structure is whether depression represents discrete types or occurs on a continuum. Nature almost universally operates on the basis of continuums, whereas human perception favors discrete categories. This reality might be formalized into a 'continuum principle': natural phenomena tend to occur on a continuum, and any instance of hypothesized discreteness requires unassailable proof. Research evidence for discrete types falls far short of this standard, with most evidence supporting a continuum. However, quantitative variation can yield qualitative differences as an emergent property, fostering the appearance of discreteness. Depression as a continuum is best characterized by duration and severity dimensions, with the latter understood in terms of depressive inhibition. In the absence of some degree of cognitive, emotional, social, and physical inhibition, depression should not be diagnosed. Combining the dimensions of duration and severity provides an optimal way to characterize the quantitative and related qualitative aspects of depression and to describe the overall degree of dysfunction. The presence of other symptom types occurs when anxiety, hypomanic/manic, psychotic, and personality continuums interface with the depression continuum.

Platelet 5-HT(1A) receptor correlates with major depressive disorder in drug-free patients

The platelet serotonergic system has potential biomarker utility for major depressive disorder (MDD). In the present study, platelet expression of 5-HT1A receptors and serotonin transporter (SERT) proteins, and serotonin (5-HT) and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) were quantified in 53 patients with MDD and 22 unaffected controls. All were drug-free, non-smokers and had no other psychiatric and cardiovascular comorbidity. The severity of depression symptoms was evaluated using the 17-item Hamilton Depression Rating Scale (HAMD-17) and the Self-rating Depression Scale (SDS). Patients with MDD had significantly higher expression of platelet 5-HT1A receptors but significantly lower contents of platelet 5-HT, platelet-poor plasma (PPP) 5-HT and PPP 5-HIAA compared to healthy controls, and this was correlated with the severity of depression. SERT expression did not differ between the two groups. Correlation analysis confirmed a strong, inverse relationship between the 5-HT1A receptor expression and the 5-HT and 5-HIAA levels. Thus overexpression of platelet 5-HT1A receptors and reduced 5-HT tone may function as a peripheral marker of depression.

The interdependence of subtype and severity: contributions of clinical and neuropsychological features to melancholia and non-melancholia in an outpatient sample

Major depressive disorder is often considered to be a homogenous disorder that changes in terms of severity; however, the presence of distinct subtypes and a variety of presenting symptoms suggests much heterogeneity. Aiming to better understand the relationship between heterogeneity and diagnosis we used an exploratory approach to identify subtypes of depression on the basis of clinical symptoms and neuropsychological performance. Cluster analysis identified two groups of patients distinguished by level of cognitive dysfunction with the more severe cluster being associated with melancholic depression. While the relationship between cluster and subtype was significant, only 58% of melancholic patients were assigned to cluster 1 (the more severe cluster) and 66% of non-melancholic patients assigned to cluster 2. Subtypes also displayed a distinctive profile of impairment such that melancholic patients (n = 65) displayed more variability in attention while non-melancholic patients (n = 59) displayed memory recall impairment. While melancholia and non-melancholia are associated with a more severe and less severe form of depression respectively, findings indicate that differences between melancholia and non-melancholia are more than simple variation on severity. In summary, findings provide support for the heterogeneity of depression.

Importance of studying the contributions of early adverse experience to neurobiological findings in depression

Almost four decades of intensive research have sought to elucidate the neurobiological bases of depression. Epidemiological studies have revealed that both genetic and environmental factors contribute to the risk for depression. Adverse early-life experiences influence neurobiological systems within genetic limits, leading to the neurobiological and behavioral manifestations of depression. We summarize the burgeoning evidence concerning a pre-eminent role of early adverse experience in the pathogenesis of depression. The available data suggest that (1) early adverse experience contributes to the pathophysiology of depression, (2) there are neurobiologically different subtypes of depression depending on the presence or absence of early adverse experience, likely having confounded previous research on the neurobiology of depression, and (3) early adverse experience likely influences treatment response in depression. Classification of depression based on developmental and neurobiological features will likely considerably improve future research in the field of depression, and might lead to optimized treatment strategies that directly target different neurobiological pathways to depression.

Disordered personality style: higher rates in non-melancholic compared to melancholic depression

OBJECTIVE

We test whether there is differential representation of disordered personality function across melancholic and non-melancholic depressive sub-types, with levels of differentiation examined against differing sub-typing measures.

METHOD

In a sample of 245 subjects meeting criteria for a non-psychotic major depressive episode lasting less than 2 years, we examine for differential rates of disordered personality style across melancholic and non-melancholic depression, using four differing sub-typing measures (i.e., DSM-III-R and DSM-IV criteria, Newcastle Index, and the CORE measure). Disordered personality was assessed by psychiatrist ratings of 15 differing personality styles underpinning disorder classes, and several parameters and domains that reflect the arenas whereby disordered personality may be manifested.

RESULTS

However defined, those with non-melancholic depression were distinctly more likely to rate as showing disordered personality function, with over-representation to an avoidant personality disorder style being the most consistently and strongly identified personality disorder class. Because of limitations to several of the sub-typing measures, we focus on the DSM-IV system. Discriminant function analyses indicated that those so identified as having non-melancholic depression were significantly more likely to rate as having avoidant and schizoid personality styles. A principal components analysis of our 15 differing personality disorder classes identified three molar classes corresponding to the three-cluster DSM system. Again, non-melancholic (compared to melancholic) subjects were more likely to return higher scores: in order, an 'anxious and fearful' (Cluster C) personality style, then an 'eccentric' Cluster A, and somewhat less clearly, a 'dramatic' Cluster B personality disorder style. Specificity to the non-melancholic depressive class was again suggested in relation to a large number of the parameters and domains measuring disordered personality function.

CONCLUSIONS

Disordered personality function appears distinctly more likely in non-melancholic, compared to melancholic depression.

An overview of depression-prone personality traits and the role of interpersonal sensitivity

A number of personality styles have been proposed as vulnerability traits to depression. In this paper methodological problems associated with identifying such traits are discussed. These include state effects contaminating personality scales and the issue of depressive heterogeneity. Potential depression-prone personality traits are then discussed, including obsessionality, neuroticism, dependency and cognitive dysfunction. High interpersonal sensitivity as a risk factor to depression is then discussed.

Treatment resistant depression in an Australian context. I: The utility of the term and approaches to management

The concept of "treatment resistant depression" (TRD) has generally been defined in terms of failure to respond to a standard course of somatic therapy with little reference to diagnostic sub-types or relevant psychosocial factors. In this paper we examine problems with the use of the term "treatment resistant depression" and then outline an approach to TRD employed in an Australian mood disorders unit. After discussing the need for a biopsychosocial assessment, multimodal management strategies for melancholic and non-melancholic TRD patients are described.

The Prince Henry Hospital Mood Disorders Unit

In 1985 a Mood Disorders Unit (MDU) was established at Prince Henry Hospital in Sydney as a clinical research module, linked with the psychiatric department of the University of New South Wales. There were three general objectives: first, to provide a specialized state-wide clinical service for the assessment and management of those with affective disorders, particularly treatment-resistant depression; secondly, to make a research contribution; and thirdly, to serve as an academic centre for teaching and training of undergraduate and postgraduate students from a variety of disciplines.

Old data, new interpretation: a re-analysis of Sir Aubrey Lewis' M.D. thesis

Sir Aubrey Lewis studied 61 depressives in considerable detail, principally cross-sectionally but also by reviewing progress. He concluded that he could find no qualitative distinctions between the depressed patients and thus established himself as a strong and influential advocate of the unitary view of depression (i.e. that depression varies dimensionally, not categorically). Subsequently, Kiloh & Garside (proponents of the binary view of two depressive 'types') coded the Lewis data and undertook a principal components analysis. They claimed success in distinguishing 'endogenous' and 'neurotic' depressive types within Lewis' sample. In this paper we re-analyse the data set using both a latent class categorical approach and mixture analyses. We suggest that any demonstration of sub-types was limited by relative homogeneity of the sample (in that up to 80% had probable or possible psychotic conditions), and by Lewis rating a number of important features (e.g. delusions) dimensionally rather than categorically. Nevertheless, we identify one categorical class (essentially an agitated psychotic depressive condition) and a residual (presumably heterogeneous) class. The presence of those two classes was supported by demonstrating bimodality in composite scores derived from the fourteen differentiating clinical features (and not evident when all clinical features were considered), and formally confirmed by mixture analyses. Membership of the categorical class was determined principally by psychotic features (delusions and hallucinations) and by objectively-judged psychomotor disturbance, and we consider the nature of that 'class'. Lewis' data set is unusual (in having self-report and observationally rated data), and historically important in demonstrating that conclusions may depend on the choice of variables examined and analytical approaches.