Structural and functional models of depression: from sub-types to substrates

A study of intensity dependence of the auditory evoked potential (IDAEP) in medicated melancholic and non-melancholic depression

BACKGROUND

Major Depressive Disorder is widely recognised to be a heterogeneous syndrome with numerous depressive phenotypes, one of which is melancholic depression. Patients with melancholic depression exhibit treatment responses and outcomes that differ from patients with non-melancholic depression. The current study aimed to assess whether differences existed between melancholic and non-melancholic subtypes of depression, as measured by the event related potential, intensity dependence of the auditory evoked potential (IDAEP).

METHODS

IDAEP was assessed in 14 melancholic and 13 non-melancholic depressed subjects and 14 controls.

RESULTS

The melancholic patients had a significantly shallower IDAEP slope than the non-melancholic patients not explained by depression severity or age.

LIMITATIONS

Antidepressants were taken by all patients in this study and the effect of continual use of these drugs on the IDAEP slopes has yet to be confirmed.

CONCLUSIONS

These results provide support for neurobiological differences between melancholic and non-melancholic depressive subtypes. Melancholic depression may be characterized by ongoing over function of the serotonin system in spite of medication treatment.

Antioxidative enzymes and increased oxidative stress in depressive women

OBJECTIVES

To investigate the activities of the main antioxidative enzymes and oxidative stress in women with depressive disorder (DD).

METHODS

In 35 drug-naive women with DD and 35 age matched healthy women enzymes superoxide dismutase (CuZnSOD), catalase (CAT), glutathione peroxidase (GPX1), glutathione reductase (GR) and paraoxonase (PON1), concentrations of conjugated dienes (CD), reduced glutathione (GSH) and anthropometric and clinical data were investigated.

RESULTS

Women with DD were found to have decreased activities of GPX1 (p<0.05), decreased concentrations of GSH (p<0.05), and increased activities of GR (p<0.05), CuZnSOD (p<0.001), and concentrations of CD (p<0.05). Activity of GPX1 was positively correlated with concentration of GSH (p<0.05). Concentrations of CD were positively correlated with TG (p<0.01).

CONCLUSION

Our set of depressive women was characterized by changes indicating an increased oxidative stress, as well as by certain features of metabolic syndrome.

Clinical practice recommendations for depression

OBJECTIVE

To provide clinically relevant evidence-based recommendations for the management of depression in adults that are informative, easy to assimilate and facilitate clinical decision making.

METHOD

A comprehensive literature review of over 500 articles was undertaken using electronic database search engines (e.g. MEDLINE, PsychINFO and Cochrane reviews). In addition articles, book chapters and other literature known to the authors were reviewed. The findings were then formulated into a set of recommendations that were developed by a multidisciplinary team of clinicians who routinely deal with mood disorders. The recommendations then underwent consultative review by a broader advisory panel that included experts in the field, clinical staff and patient representatives.

RESULTS

The clinical practice recommendations for depression (Depression CPR) summarize evidence-based treatments and provide a synopsis of recommendations relating to each phase of the illness. They are designed for clinical use and have therefore been presented succinctly in an innovative and engaging manner that is clear and informative.

CONCLUSION

These up-to-date recommendations provide an evidence-based framework that incorporates clinical wisdom and consideration of individual factors in the management of depression. Further, the novel style and practical approach should promote uptake and implementation.

Dual- and triple-acting agents for treating core and co-morbid symptoms of major depression: novel concepts, new drugs

The past decade of efforts to find improved treatment for major depression has been dominated by genome-driven programs of rational drug discovery directed toward highly selective ligands for nonmonoaminergic agents. Selective drugs may prove beneficial for specific symptoms, for certain patient subpopulations, or both. However, network analyses of the brain and its dysfunction suggest that agents with multiple and complementary modes of action are more likely to show broad-based efficacy against core and comorbid symptoms of depression. Strategies for improved multitarget exploitation of monoaminergic mechanisms include triple inhibitors of dopamine, serotonin (5-HT) and noradrenaline reuptake, and drugs interfering with feedback actions of monoamines at inhibitory 5-HT(1A), 5-HT(1B) and possibly 5-HT(5A) and 5-HT(7) receptors. Specific subsets of postsynaptic 5-HT receptors mediating antidepressant actions are under study (e.g., 5-HT(4) and 5-HT(6)). Association of a clinically characterized antidepressant mechanism with a nonmonoaminergic component of activity is an attractive strategy. For example, agomelatine (a melatonin agonist/5-HT(2C) antagonist) has clinically proven activity in major depression. Dual neurokinin(1) antagonists/5-HT reuptake inhibitors (SRIs) and melanocortin(4) antagonists/SRIs should display advantages over their selective counterparts, and histamine H(3) antagonists/SRIs, GABA(B) antagonists/SRIs, glutamatergic/SRIs, and cholinergic agents/SRIs may counter the compromised cognitive function of depression. Finally, drugs that suppress 5-HT reuptake and blunt hypothalamo-pituitary-adrenocorticotrophic axis overdrive, or that act at intracellular proteins such as GSK-3beta, may abrogate the negative effects of chronic stress on mood and neuronal integrity. This review discusses the discovery and development of dual- and triple-acting antidepressants, focusing on novel concepts and new drugs disclosed over the last 2 to 3 years.

Improving the prediction of treatment response in depression: integration of clinical, cognitive, psychophysiological, neuroimaging, and genetic measures

Antidepressants are important in the treatment of depression, and selective serotonin reuptake inhibitors are first-line pharmacologic options. However, only 50% to 70% of patients respond to first treatment and <40% remit. Since depression is associated with substantial morbidity, mortality, and family burden, it is unfortunate and demanding on health resources that patients must remain on their prescribed medications for at least 4 weeks without knowing whether the particular antidepressant will be effective. Studies have suggested a number of predictors of treatment response, including clinical, psychophysiological, neuroimaging, and genetics, each with varying degrees of success and nearly all with poor prognostic sensitivity and specificity. Studies are yet to be conducted that use multiple measures from these different domains to determine whether sensitivity and specificity can be improved to predict individual treatment response. It is proposed that a focus on standardized testing methodologies across multiple testing modalities and their integration will be crucial for translation of research findings into clinical practice.

Use of neuromelanin-sensitive MRI to distinguish schizophrenic and depressive patients and healthy individuals based on signal alterations in the substantia nigra and locus ceruleus

BACKGROUND

We investigated alterations in the substantia nigra pars compacta (SNc) and locus ceruleus (LC) in schizophrenic and depressive patients by using a neuromelanin-sensitive magnetic resonance imaging (MRI) technique that enables direct visualization of these nuclei and examined whether this technique could distinguish between these disorders and healthy subjects.

METHODS

Using a neuromelanin-sensitive T1-weighted MRI technique, we examined 20 schizophrenia patients, 18 depressive patients, and 34 healthy control subjects. The signal intensities of the areas corresponding to the SNc and LC were measured, and the contrast ratios (CR) to the adjacent white matter were calculated.

RESULTS

The CR of the SNc was significantly higher in schizophrenic patients (22.6 +/- 5.6) than in depressive patients (19.2 +/- 4.7) and healthy control subjects (19.6 +/- 3.8), whereas the CR of the LC in depressive patients (7.7 +/- 2.4) was significantly lower than that in healthy control subjects (11.0 +/- 3.9) and schizophrenic patients (10.0 +/- 3.1). Further, the difference in the CR between the SNc and LC was significantly greater in schizophrenic patients (12.6 +/- 6.7) than in control subjects (8.6 +/- 4.1).

CONCLUSIONS

Neuromelanin-sensitive MRI enables visualization of alterations in the SNc and LC that are observed in schizophrenia and depression.

Examining age effects on prototypic melancholic symptoms as a strategy for refining definition of melancholia

BACKGROUND

Melancholic depression appears to have a later age of onset than the non-melancholic disorders, and its phenotypic picture also appears to change with age. The latter phenomenon allows clarification of key symptoms of melancholia by examining for age effects on putative melancholic symptoms, thus enabling identification and refinement of the melancholic sub-type.

METHODS

We studied 158 patients receiving a diagnosis of unipolar depression (65 melancholic: 93 non-melancholic), dichotomised by age and with a higher representation of those with melancholia in the older age band. The severity of individual DSM-IV-TR melancholic candidate symptom constructs were quantified across age groups and diagnostic sub-type.

RESULTS

Symptom constructs identified as most clearly associated with age effects in those with melancholia were anhedonia, non-reactivity, diurnal mood variation and, to a lesser degree, psychomotor slowing. When melancholic and non-melancholic patients were compared, non-reactivity, psychomotor slowing and diurnal mood variation were the most differentiating in the older age group.

CONCLUSIONS

The capacity of certain symptoms to mark the changing phenotypic expression of melancholia with age may not only assist refined definition of melancholia but inform about underlying causes and, of key importance, explain the suggested differential impact of narrow-action and broad-action antidepressant on those with melancholia across differing age groups.

Psychomotor symptoms in depression: a diagnostic, pathophysiological and therapeutic tool

BACKGROUND

Psychomotor disturbances have been described repeatedly over many centuries. More recently, Sobin and Sackeim [Sobin, C., Sackeim, H.A., 1997. Psychomotor symptoms of depression. Am. J. Psychiatry. 154, 4-17.] discussed the relevance of psychomotor symptoms in depression in an extensive review. Since their report, new pathophysiological, diagnostic and therapeutic findings have been published. In the current review of the recent literature, we aim to argue the importance of psychomotor symptoms in depression and propose directions for future research.

METHOD

A review of all the relevant reports on this topic, published between 1996 and 2006, was conducted.

RESULTS

Several assessment methods demonstrate the diagnostic and pathophysiological significance of psychomotor symptoms. Antidepressants show differential effects on psychomotor performance and findings concerning the symptoms' predictive capacity for clinical response are contradictory. Numerous imaging studies as well as studies on the neurotransmitter systems and the HPA-axis contribute to the elucidation of the neurobiological processes underlying impaired psychomotor functioning in depression.

CONCLUSIONS

Psychomotor disturbances are of great diagnostic significance for the depressive subtype of melancholia. To enhance the conceptualisation of the construct 'psychomotor' a standardised battery for their assessment is recommended. As to the symptoms' predictive therapeutic power, to date research into functional outcome and studies applying objective experimental assessment methods are lacking. Moreover, the reported pathophysiological importance of dopamine for 'retarded depression' still warrants translation to the daily practice.

The development of valid subtypes for depression in primary care settings: a preliminary study using an explanatory model approach

A persistent theme in the debate on the classification of depressive disorders is the distinction between biological and environmental depressions. Despite decades of research, there remains little consensus on how to distinguish between depressive subtypes. This preliminary study describes a method that could be useful, if implemented on a larger scale, in the development of valid subtypes of depression in primary care settings, using explanatory models of depressive illness. Seventeen depressed Hispanic patients at an inner city general practice participated in explanatory model interviews. Participants generated illness narratives, which included details about symptoms, cause, course, impact, health seeking, and anticipated outcome. Two distinct subtypes emerged from the analysis. The internal model subtype was characterized by internal attributions, specifically the notion of an "injured self." The external model subtype conceptualized depression as a reaction to life situations. Each subtype was associated with a distinct constellation of clinical features and health seeking experiences. Future directions for research using explanatory models to establish depressive subtypes are explored.

Patient satisfaction with the Black Dog Institute Depression Clinic

OBJECTIVE

The aim of this paper is to report on patient satisfaction with the Black Dog Institute Depression Clinic, a tertiary referral service providing assessment and treatment advice to patients with mood disorders.

METHOD

Patients who attended the Depression Clinic over the period 2006-2007 received questionnaires in the mail assessing satisfaction with the services received. Of the 321 patients attending, 114 (35%) replied. Results from 110 patients were subsequently analysed.

RESULTS

Overall, patients were very satisfied with the services received. However, a number of priority areas were identified including provision of information about diagnosis, causal factors and treatment options; managing patient expectations about services offered; the need for improvement of communication between patient and psychiatrist; and the need for adequate de-briefing for those who receive an unexpected or differing diagnosis.

CONCLUSIONS

Patient satisfaction is a central component in shaping clinical service development to ensure delivery of effective health care. Findings from this study have implications for the improved delivery of psychiatric services.

Reduced signal of locus ceruleus in depression in quantitative neuromelanin magnetic resonance imaging

We used a neuromelanin-magnetic resonance imaging technique to investigate abnormalities in the locus ceruleus in depression. We examined 20 patients with major depression and 43 age-matched controls using a 3 T scanner with a neuromelanin-sensitive sequence. The signal intensities of the areas corresponding to the rostral, middle, and caudal portions of the locus ceruleus were measured, and the contrast ratio relative to the adjacent pontine tegmentum was calculated. In controls, the contrast ratio in the middle portion was higher than in the rostral and caudal areas. In patients, contrast ratios in the rostral and middle portions were significantly decreased in comparison with controls, suggesting dysfunction of the ascending noradrenergic system. Neuromelanin-magnetic resonance imaging can be used to visualize abnormalities in the locus ceruleus of depressive patients.

A growth in bipolar disorder?

OBJECTIVE

This case report suggests that screening of patients with psychiatric symptoms using modern neuroimaging can help identify organic causes of mental illness.

METHOD

A single case study was reported.

RESULTS

We report the case of a 25-year-old woman with a recent diagnosis of bipolar II disorder having an magnetic resonance imaging (MRI) scan as part of a research project that reveals an intraventricular brain tumour. The latter is most likely the cause of her irritability and 'hypomanic' symptoms and is defined anatomically using diffusion tensor imaging and structural and functional imaging using MRI and positron emission tomography.

CONCLUSION

The lesion in this individual case most probably produces mood symptoms by impinging upon the fornix, a component of the limbic system. However, more generally, the increase in diagnosis of bipolar disorder has to be tempered against alternate causes of similar symptoms and necessitates vigilance of potential organic mechanisms.

Does dopamine dysfunction drive depression?

OBJECTIVE

To examine the evidence that dopamine (DA) dysfunction contributes to melancholic depression.

METHOD

Database (EMBASE, PsychLit and MEDLINE) searches using relevant key words were conducted and citations were scrutinized.

RESULTS

In this paper, we assume that the definition of melancholia is contingent upon the presence of psychomotor disturbance (PMD). In melancholic depression PMD comprises both a cognitive and motor component and DA is found to be important in both. DA neurotransmission modulates cognition in particular in attention, adaptation and motivational processes and has a pivotal role in motor function.

CONCLUSION

DA is a credible aetiological candidate for the PMD in melancholic depression. However, melancholia needs first to be characterized both clinically and in terms of its pathophysiology. In this regard, illnesses such as bipolar depression and Parkinson's disease warrant consideration as they provide suitable models of both the cognitive and motor aspects of PMD, and hold the necessary markers to better define melancholia.

Through a glass darkly: the disutility of the DSM nosology of depressive disorders

OBJECTIVE

To demonstrate that the dimension-weighted DSM-IV model for classifying the depressive disorders lacks utility.

METHOD

The logical flaws in classifying the depressive disorders with any severity-based model (which underpin both the DSM-IV and ICD-10 systems) are noted. Integral definitional limitations to the DSM-IV definition of key depressive disorders are identified. It is argued that the DSM-IV classificatory system lacks utility for providing information on etiology and preferential management strategies. An alternative subtyping model is considered.

RESULTS

It is asserted that, in practice, the DSM-IV model and criteria lack explanatory power and compromise research and clinical practice.

CONCLUSIONS

It is hoped that this article evokes wider debate about modelling and classifying the depressive disorders.

The Black Dog Institute Depression Clinic: a subtyping model in practice

OBJECTIVE

The new Black Dog Institute Depression Clinic adopts a novel clinical service model that argues for the importance of clinically defining separate mood disorders in order to apply specific management strategies. This paper describes clinic nuances and the impact on diagnosis and management for the first 100 patients assessed.

METHOD

Patients are assessed via a computerized structured self-report program, a semistructured interview undertaken by a psychiatrist and a colloquium involving several practitioners where diagnostic decisions are formulated. A detailed report with treatment recommendations, incorporating psychiatric and psychological perspectives, is sent to the referring clinician. Such data are examined in this report.

RESULTS

We offered a differing diagnostic and treatment paradigm for nearly 90% of those diagnosed with a primary mood disorder. Difficulties encountered by referring practitioners are highlighted and the need for an alternative diagnostic and management model is discussed.

CONCLUSIONS

A subtyping diagnostic management model has the capacity to advance treatment outcome, but requires validation. Our future research will assess the comparative utility of the subtyping model in clinical and research arenas.

Negative symptoms: A review of schizophrenia, melancholic depression and Parkinson's disease

Negative symptoms generally refer to a reduction in normal functioning. In schizophrenia they encompass apathy, anhedonia, flat affect, avolition, social withdrawal and, on some accounts, psychomotor retardation. Negative symptoms have been identified in other psychiatric disorders, including melancholic depression, and also in neurological disorders, such Parkinson's disease. Achieving a better understanding of negative symptoms constitutes a priority in mental health. Primarily, negative symptoms represent an unrelenting, intractable and disabling feature for patients, often amounting to a severe burden on families, carers and the patients themselves. Identifying and understanding subgroups within disorders may also contribute to the clinical care and scientific understanding of the pathophysiology of these disorders. The purpose of this paper is to review the current literature on negative symptoms in schizophrenia and explore the idea that negative symptoms may play an important role not only in other psychiatric disorders such as melancholic depression, but also in neurological disorders, such as Parkinson's disease. In each disorder negative symptoms manifest with similar motor and cognitive impairments and are associated with comparable neuropathological and biochemical findings, possibly reflecting analogous impairments in the functioning of frontostriatal-limbic circuits.

Why am I depressed?: An investigation of whether patients' beliefs about depression concur with their diagnostic subtype

We investigated whether patients' beliefs about the causes of their depression concurred with their diagnostic subtype. Depressed patients (N = 196) attending a tertiary referral clinic completed a questionnaire regarding putative biological and nonbiological causes of their depression. Subtyping diagnoses of melancholic or nonmelancholic depression were made. Patients with nonmelancholic depression were more likely to attribute nonbiological factors as the cause of their depression than those with melancholic depression, whereas patients with melancholic depression were no more likely to attribute biological factors as the cause of their depression. Patients can distinguish differing causes of depression. The implications of the findings for the current classificatory systems of depression are discussed.

Do antidepressants cure or create abnormal brain states?

Moncrieff and Cohen argue that psychotropic drugs create abnormal states that may co-incidentally relieve symptoms of mental illness.

Ocular motor differences between melancholic and non-melancholic depression

BACKGROUND

Major depressive disorder may be a heterogeneous disorder, yet melancholic depression is the most consistently described subtype, regarded as qualitatively different to non-melancholic depression in terms of cognitive and motor impairments. Eye movement studies in depression are infrequent and findings are inconclusive.

METHODS

This study employed a battery of saccadic eye movement tasks to explore reflexive saccades, as well as higher order cognitive aspects of saccades including inhibitory control and spatial working memory. Nineteen patients with major depressive disorder (9 melancholic; 10 non-melancholic) and 15 healthy controls participated.

RESULTS

Differences were revealed between melancholic and non-melancholic patients. Melancholia was associated with longer latencies, difficulty increasing peak velocities as target amplitudes increased, and hypometric primary saccades during the predictable protocol. In contrast, the non-melancholic depression group performed similarly to controls on most tasks, but saccadic peak velocity was increased for reflexive saccades at larger amplitudes.

LIMITATIONS

Most patients were taking antidepressant medication.

CONCLUSIONS

The latency increases, reduced peak velocity and primary saccade hypometria with more severe melancholia may be explained by functional changes in the fronto-striatal-collicular networks, related to dopamine dysfunction. In contrast, the serotonergic system plays a greater role in non-melancholic symptoms and this may underpin the observed increases in saccadic peak velocity. These findings provide neurophysiological support for functional differences between depression subgroups that are consistent with previous motor and cognitive findings.

Multi-target strategies for the improved treatment of depressive states: Conceptual foundations and neuronal substrates, drug discovery and therapeutic application

Major depression is a debilitating and recurrent disorder with a substantial lifetime risk and a high social cost. Depressed patients generally display co-morbid symptoms, and depression frequently accompanies other serious disorders. Currently available drugs display limited efficacy and a pronounced delay to onset of action, and all provoke distressing side effects. Cloning of the human genome has fuelled expectations that symptomatic treatment may soon become more rapid and effective, and that depressive states may ultimately be "prevented" or "cured". In pursuing these objectives, in particular for genome-derived, non-monoaminergic targets, "specificity" of drug actions is often emphasized. That is, priority is afforded to agents that interact exclusively with a single site hypothesized as critically involved in the pathogenesis and/or control of depression. Certain highly selective drugs may prove effective, and they remain indispensable in the experimental (and clinical) evaluation of the significance of novel mechanisms. However, by analogy to other multifactorial disorders, "multi-target" agents may be better adapted to the improved treatment of depressive states. Support for this contention is garnered from a broad palette of observations, ranging from mechanisms of action of adjunctive drug combinations and electroconvulsive therapy to "network theory" analysis of the etiology and management of depressive states. The review also outlines opportunities to be exploited, and challenges to be addressed, in the discovery and characterization of drugs recognizing multiple targets. Finally, a diversity of multi-target strategies is proposed for the more efficacious and rapid control of core and co-morbid symptoms of depression, together with improved tolerance relative to currently available agents.

Treatment-resistant depression: resistant to definition?

OBJECTIVE

To better define treatment-resistant depression (TRD) so as to assist clinical management and refine treatment guidelines.

METHOD

In this study, we examine a broad range of clinical variables in depressed patients (n=196) referred to a tertiary referral Mood Disorders Unit (MDU). Information was collected from patients, referrers and assessors over a period of 32 months and included evaluations of treatments, treatment resistance and related variables. Data were analysed across trichotomized 'high', 'low' and 'no' treatment resistance groupings of patients.

RESULTS

A significantly greater proportion of patients with melancholia were amongst the high TRD group, and this was consistent across different strategies for evaluating melancholia.

CONCLUSION

Melancholia perhaps provides a prototypic TRD subset that perhaps reflects some innate aspects of melancholic depression or factors such as the impact of ageing. Research into TRD is needed to both replicate this finding and perhaps explicate it further.