Do psychotic, minor and intermittent depressive disorders exist on a continuum?

Stable abnormalities of contrast discrimination sensitivity in subthreshold depression: A longitudinal study

Subthreshold depression (StD), as a subclinical state, is highly prevalent and increases the risk for developing major depressive disorder (MDD). Although several studies have reported deficits of contrast sensitivity in MDD patients, it is unclear whether individuals with StD could demonstrate deficits of contrast sensitivity and whether the deficits could remain stable over time. Here we used a contrast discrimination task (a suprathreshold task) and a contrast detection task (a near-threshold task) to compare contrast sensitivity of the StD group with that of matched non-depressed controls. For each task, a spatial four-alternative forced-choice method and a psychophysical QUEST procedure were used to measure contrast discrimination threshold or contrast detection threshold. Participants performed an initial assessment and a follow-up assessment 4 months later. Compared to the non-depressed controls, individuals with StD demonstrated reduced contrast discrimination sensitivity, not only at the initial assessment but also at the follow-up assessment, indicating a stable abnormality. Contrast discrimination thresholds at the initial assessment did not predict changes of depression symptom severity over time. For contrast detection sensitivity, there was no significant difference between the StD group and non-depressed controls. We concluded that contrast discrimination testing might provide a trait-dependent biomarker for depression.

Subthreshold depression may exist on a spectrum with major depressive disorder: Evidence from gray matter volume and morphological brain network

BACKGROUND

Subthreshold depression (StD) is a prevalent condition that may increase the risk of incident major depressive disorder (MDD). However, the relationship between StD and MDD remains unclear.

METHODS

A total of 153 adult subjects, including 53 drug-naive MDD, 50 StD and 50 healthy control (HC) subjects, underwent a T1-weighted magnetic resonance imaging scan, and the gray matter volume (GMV) alterations among the three groups were quantitatively analyzed using voxel-based morphometry (VBM). Then, to capture the whole-brain connectivity characteristics, we constructed morphological brain networks (MBN) based on the similarity among brain regions of individual VBM images and compared the network connection strengths among the three groups.

RESULTS

The StD and MDD subjects had similar patterns of GMV reductions in the orbitofrontal cortex and left temporal gyrus, although the magnitude of the reductions was smaller in StD subjects. Moreover, a total of 21 morphological connections were significantly different among the three groups. For the majority of the different connections (15/21), the connection strength of the StD group took an intermediate position between that of the MDD and HC groups.

LIMITATIONS

There is still a lack of a consistent definition of StD, and the age range of the subjects in this study was wide. Meanwhile the mechanisms and biological significance of the MBN remains to be clarified.

CONCLUSIONS

These results may support the hypothesis that depression is better expressed as a spectrum and that StD exists on a spectrum with MDD.

Subthreshold Psychiatric Psychopathology in Functional Gastrointestinal Disorders: Can It Be the Bridge between Gastroenterology and Psychiatry?

Background and Aims

Functional gastrointestinal disorders (FGDs) are multifactorial disorders of the gut-brain interaction. This study investigated the prevalence of Axis I and spectrum disorders in patients with FGD and established the link between FGDs and psychopathological dimensions.

Methods

A total of 135 consecutive patients with FGD were enrolled. The symptoms' severity was evaluated using questionnaires, while the psychiatric evaluation by clinical interviews established the presence/absence of mental (Diagnostic and Statistical Manual-4th edition, Axis I Diagnosis) or spectrum disorders.

Results

Of the 135 patients, 42 (32.3%) had functional dyspepsia, 52 (40.0%) had irritable bowel syndrome, 21 (16.2%) had functional bloating, and 20 (15.4%) had functional constipation. At least one psychiatric disorder was present in 46.9% of the patients, while a suprathreshold panic spectrum was present in 26.2%. Functional constipation was associated with depressive disorders (p < 0.05), while functional dyspepsia was related to the current major depressive episode (p < 0.05). Obsessive-compulsive spectrum was correlated with the presence of functional constipation and irritable bowel syndrome (p < 0.05).

Conclusion

The high prevalence of subthreshold psychiatric symptomatology in patients with FGD, which is likely to influence the expression of gastrointestinal symptoms, suggested the usefulness of psychological evaluation in patients with FGDs.

Clinical and molecular genetics of psychotic depression

This review provides a comprehensive overview of clinical and molecular genetic as well as pharmacogenetic studies regarding the clinical phenotype of "psychotic depression." Results are discussed with regard to the long-standing debate on categorical vs dimensional disease models of affective and psychotic disorders on a continuum from unipolar depression over bipolar disorder and schizoaffective disorder to schizophrenia. Clinical genetic studies suggest a familial aggregation and a considerable heritability (39%) of psychotic depression partly shared with schizoaffective disorder, schizophrenia, and affective disorders. Molecular genetic studies point to potential risk loci of psychotic depression shared with schizoaffective disorder (1q42, 22q11, 19p13), depression, bipolar disorder, and schizophrenia (6p, 8p22, 10p13-12, 10p14, 13q13-14, 13q32, 18p, 22q11-13) and several vulnerability genes possibly contributing to an increased risk of psychotic symptoms in depression (eg, BDNF, DBH, DTNBP1, DRD2, DRD4, GSK-3beta, MAO-A). Pharmacogenetic studies implicate 5-HTT, TPH1, and DTNBP1 gene variation in the mediation of antidepressant treatment response in psychotic depression. Genetic factors are suggested to contribute to the disease risk of psychotic depression in partial overlap with disorders along the affective-psychotic spectrum. Thus, genetic research focusing on psychotic depression might inspire a more dimensional, neurobiologically and symptom-oriented taxonomy of affective and psychotic disorders challenging the dichotomous Kraepelinian view. Additionally, pharmacogenetic studies might aid in the development of a more personalized treatment of psychotic depression with an individually tailored antidepressive/antipsychotic pharmacotherapy according to genotype.

The effect of severity and personality on the psychotic presentation of major depression

The aim of the present study was to evaluate whether symptom severity or personality traits are associated with psychotic symptoms in major depression (MD), since it is still debated whether psychotic depression represents the most severe form of depression or the effect of personality structure. The study included 163 patients affected by MD who were divided into four groups on the basis of the presence/absence of melancholic features and psychotic symptoms. All subjects completed the Structured Clinical Interview for DSM-IV Disorders (SCID-IV), the Structured Clinical Interview for DSM-IV Personality Disorders (SIDP-IV) and the Hamilton Rating Scale for Depression (Ham-D). Personality was assessed after MD remission (absence of DSM-IV criteria and Ham-D score lower than 7 for at least 2 months). Psychotic symptoms were positively associated with symptom severity (higher Ham-D total score) and with paranoid and schizotypal traits and negatively related to histrionic traits. Our data support the view that the effect of paranoid-schizotypal traits and symptom severity on the presence of psychotic symptoms in MD occurs separately and they are independent of each other.

An overview of the genetics of psychotic mood disorders

This article presents a conceptual review of the genetic underpinnings of psychotic mood disorders. Both unipolar and bipolar forms of mood disorder sometimes feature psychotic symptoms. Some evidence from epidemiological research suggests that psychotic forms of mood disorder specifically might be heritable. Linkage studies of mood disorders in general have also provided some support for that notion, as have associated studies involving serotonin and dopamine genes and psychotic mood disorder. Some research suggests there might be a genetic connection between schizophrenia and bipolar disorder, undermining the Kraepelinian dichotomous classification of the psychoses. Future research should continue to examine psychotic forms of mood disorder using both epidemiological and molecular approaches.

Familial aggregation of psychotic symptoms in a replication set of 69 bipolar disorder pedigrees

We found evidence previously of familial aggregation of psychotic symptoms in 65 bipolar disorder pedigrees. This finding, together with prior evidence from clinical, family, neurobiological, and linkage studies, suggested that psychotic bipolar disorder may delineate a valid subtype. We sought to replicate this finding in 69 new bipolar disorder pedigrees. The presence of psychotic symptoms, defined as hallucinations or delusions, during an affective episode was compared in families of 46 psychotic and 23 non-psychotic bipolar I probands ascertained at Johns Hopkins for the NIMH Bipolar Disorder Genetics Initiative. There were 198 first-degree relatives with major affective disorder including 90 with bipolar I disorder. Significantly more psychotic proband families than non-psychotic proband families (76% vs. 48%) contained at least one affected relative with psychotic symptoms. Psychotic symptoms occurred in 35% of relatives of psychotic probands and in 22% of relatives of non-psychotic probands (P = 0.10). Both psychotic affective disorder generally and psychotic bipolar I disorder clustered significantly in families. These results are consistent with our prior report although the magnitude of the predictive effect of a psychotic proband is less in the replication families. Our findings provide modest support for the validity of psychotic bipolar disorder as a subtype of bipolar disorder. This clinically defined subtype may prove more homogeneous than the disorder as a whole at the level of genetic etiology and of neuropathology/pathophysiology. Families with this subtype should be used to search for susceptibility genes common to bipolar disorder and schizophrenia, and for biological markers that may be shared with schizophrenia.

Conceptual underpinnings and empirical support for the mood spectrum

This article presents an overview of the conceptual basis and empirical support for a unitary view of mood disturbance. The authors consider this general conceptualization of psychiatric disturbance as consisting of an array of related symptoms and behavioral features that define the "spectrum" of each disorder. They discuss how this conceptual framework aids in overcoming what they believe to be the false dichotomy between unipolar and bipolar mood disorders and in evaluating subthreshold and unusual presentations. They also describe the structured clinical interview and self-report instrument that they have developed to facilitate systematic assessment of the proposed mood spectrum. Finally, they summarize the clinical utility of such an approach to the description and assessment of patients with mood disorders.

The prevalence, clinical relevance, and public health significance of subthreshold depressions

Scientific evidence has accumulated during the last 15 years establishing that SD symptoms have a high prevalence in the general population and in clinically depressed patient cohorts studied cross-sectionally or followed longitudinally. The clinical relevance and public health importance of SD symptoms were confirmed when various investigators, including the authors' group at University of California, San Diego, found that SD symptoms are associated with a significant and pervasive impairment of psychosocial function when compared to no depressive symptoms. There is strong evidence that all levels of depressive symptom severity of unipolar MDD are associated with significant psychosocial impairment, which increases significantly and linearly with each increment in level of symptom severity. It is only when MDD patients are completely symptom free that psychosocial function returns to good or very good levels. The disability associated with depression is state dependent, and disability returns to good or normal levels only when all of the depressed patients' symptoms abate, because disability is present when even a few symptoms (i.e., SD symptoms) are detected. There is strong evidence during the long-term course of illness that major, minor, dysthymic, and subsyndromal symptoms wax and wane within the same patient and that these symptomatic periods are interspersed in the overall course with times when patients are remitted and symptom free. The modal longitudinal symptom status of MDD patients involves primarily subthreshold depressive symptoms, which are much more common than symptoms at the syndromal MDE level. The longitudinal systematic examination of the clinical relevance and high prevalence of SD symptoms helped establish the fact that the long-term symptomatic expression of MDD is dimensional, not categorical, in nature. Abatement of SD symptoms is of fundamental importance in defining full remission or recovery of MDEs. Ongoing residual SD symptoms during the recovery periods after an MDE are associated with psychosocial disability, more rapid MDE relapse, and a more severe chronic future course of illness, all of which indicate that when residual SD symptoms are present the MDE has not fully remitted and the disease is still active. When all depressive symptoms of an MDE abate for a minimum of 8 weeks, then full remission has been achieved. MDE remission defined in this way is associated with significant delay or even prevention of future episode relapse and a less severe, relapsing, and chronic future course. The authors submit that the research reviewed in this article heralds a new paradigm in understanding the progression of clinical depression through various overlapping stages of severity, which begin at the seemingly "subclinical" level of depressive symptoms. This conceptualization in turn dictates a public health approach, which emphasizes that treatment of MDD even at the deceptively mild levels of symptoms should be initiated or maintained.

Is clinical depression distinct from subthreshold depressive symptoms? A review of the continuity issue in depression research

Resolving whether subthreshold depressive symptoms exist on a continuum with unipolar clinical depression is important for progress on both theoretical and applied issues. To date, most studies have found that individuals with subthreshold depressive symptoms resemble cases of major depressive disorder along many important dimensions (e.g., in terms of patterns of functional impairment, psychiatric and physical comorbidity, familiality, sleeping EEG, and risk of future major depression). However, such manifest similarities do not rule out the possibility of a latent qualitative difference between subthreshold and diagnosable depression. Formal taxonomic analyses, intended to resolve the possibility of a latent qualitative distinction, have so far yielded contradictory findings. Several large-sample latent class analyses (LCA) have identified latent clinical and nonclinical classes of unipolar depression, but LCA is vulnerable to identification of spurious classes. Paul Meehl's taxometric methods provide a potentially conservative alternative way to identify latent classes. The one comprehensive taxometric analysis reported to date suggests that self-report depression symptoms occur along a latent continuum but exclusive reliance on self-report depression measures and incomplete information regarding sample base rates of depression makes it difficult to draw strong inferences from that report. We conclude that although most of the evidence at this time appears to favor both a manifest and latent continuum of unipolar depression symptomatology, several important issues remain unresolved. Complete resolution of the continuity question would be speeded by the application of both taxometric techniques and LCA to a single large sample with a known base rate of lifetime diagnosed depressives.

Minor depressive disorder in the context of miscarriage

BACKGROUND

Although minor depressive disorder is of considerable clinical and public health importance, it has received limited research attention relative to major depressive disorder. This study examines the incidence rate and relative risk for minor depressive disorder following miscarriage.

METHODS

Using a cohort design we tested whether miscarrying women are at increased risk for an episode of minor depression (diagnosed based on research criteria proposed in Appendix B of DSM-IV) in the 6 months following loss. The miscarriage cohort consisted of women attending a medical center for spontaneous abortion (n=229); the comparison group was a population-based cohort of women drawn from the community (n=230).

RESULTS

Among miscarrying women, 5.2% experienced an episode of minor depression, compared with 1.0% of community women. The overall relative risk for an episode of minor depression for miscarrying women was 5.2 (95% confidence interval, 1.2-23.6). Relative risk did not vary by length of gestation at the time of loss or attitude toward the pregnancy. The majority of episodes in miscarrying women began within 1 month following loss.

LIMITATIONS

Minor depression was relatively rare in both study cohorts. The resulting limits on statistical power reduced our ability to identify factors, such as sociodemographic or reproductive history variables that might moderate the effect of miscarriage on risk for minor depression.

CONCLUSIONS

These results, in the context of prior work showing increased risks of major depression and depressive symptoms following miscarriage, lend some support to the conceptualization of minor depressive disorder as part of a continuum of symptom severity. Miscarrying women should be evaluated for depression at their follow-up medical visits.

Subthreshold depressive and anxiety disorders in the elderly

The aims of the present study were to compare the current and lifetime prevalences for major and subthreshold affective disorders in elderly subjects in the general population, to assess the influence of demographic variables on prevalence rates, and to examine co-morbidity between these disorders. Major and subthreshold disorders were diagnosed in 286 subjects (aged >/= 60 years). Four-point-nine percent of the subjects had a lifetime diagnosis of major depression, 31.8% either minor or recurrent brief depression, 6.6% a major anxiety disorder, and 18.5% a subthreshold anxiety disorder. The risk for current and lifetime subthreshold anxiety was higher in females than in males, the lifetime prevalence for subthreshold anxiety disorders was increased in elderly subjects and subjects with low professional levels. Increased co-morbidity between major and subthreshold depressive and anxiety disorders could not be observed. In the elderly, subthreshold depressive and anxiety disorders are frequent, more so than major affective disorders. The presence of subthreshold anxiety disorders, but not subthreshold depression, is influenced by age, gender, and previous professional level. Further research focusing on detection, evaluation of risk factors and the relevance for the quality of life in the elderly general population is needed.

Pleomorphic expressions of unipolar depressive disease: summary of the 1996 CINP President's Workshop

Data presented during the 1996 CINP President's Workshop supported the conclusion that unipolar major depressive disorder (MDD) is a pleomorphic mood disorder consisting of a cluster of depressive subtypes existing in a relatively homogeneous symptomatic clinical continuum, extending from subsyndromal depressive symptomatology (SSD) through minor depressive episode, dysthymic disorder, major depressive episode and double depression. This indicates that common unipolar depressive subtypes can be conceptualized as alternate forms or different symptomatic phases of the same parent illness. Although there appears to be great overlap across time in the symptomatological expressions of these clinical depressive subtypes, they may be derived from different etiological and genetic factors. The one exception may be major depressive episode with psychotic features, which exists on a severity continuum with other subtypes of unipolar MDD, but does not appear to be on a symptomatic continuum with dysthymic, subsyndromal or minor depressions. By contrast, SSD and minor depressive disorder represent clinically significant depressive subtypes, which are commonly observed during the course of illness of patients with unipolar major depressive illness. Compared to no depressive symptoms, SSD is associated with harmful dysfunction, as evidenced by significant increases in psychosocial impairment, signifying that SSD is an active, inter-episode disease state of unipolar major depressive disorder. Finally, SSD, possibly jointly with subthreshold anxiety symptoms, may also represent potent risk factors for rapid depressive episode relapse. In the aggregate, these findings and conclusions have broad and important implications for diagnostic and treatment strategies of unipolar MDD.