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Depression is common and under-recognised in neurological disorders. The evidence is that it can be treated and that this improves outcomes.
There is a steady accumulation of evidence from studies in community, primary care, neurological and neurorehabilitative settings that depression is a common comorbidity with a wide range of central nervous system conditions. Yet, the rate of recognition and treatment of depression in neurological settings remains worryingly low.1 While the reasons for low rates of detection and treatment of depression could be numerous, one of the factors which may contribute towards low rates of treatment could be a lack of evidence to support the treatment of depression in neurological patients. In Price et al2 (see page 914), a robust meta-analysis of RCTs shows that treatment with antidepressants in patients with neurological disorders is associated with twice the chance of remission 6–8 weeks after the onset of treatment.
The importance of early detection and treatment of depression in neurological settings is supported by growing evidence. The effect of depression on quality of life of patients with neurological conditions is now well recognised.3 4 Depression is also shown to affect the duration of hospital stay, engagement in treatment and outcome of treatment including residual disability and mortality. Depression could also be an independent predictor of neurological disorders such as stroke, Parkinson's disease and dementia, and could be associated with non-response to treatment.
So, what could be the barriers, and what can be done about them? Clinicians in neurological settings may not be confident in diagnosing depression reliably. This may partly be due to a lack of adequate psychiatric training available to neurologists, but even trained general psychiatrists often confess that they find it hard to diagnose depression confidently in neurological patients. Often the presentation of depression in patients with neurological conditions has a significant overlap with underlying features of neurological condition or side-effects of medications. Diagnostic and Statistical Manual of Mental Disorders IV and Tenth Revision of the International Classification of Diseases criteria for depression may not be adequately met due to atypical presentations, limiting the utility of these diagnostic systems in neurological settings.
Patients and carers may not wish to report depressive symptoms to neurologists, feeling that they may not be interested in knowing about emotional problems. They may worry about additional stigma that may be attached to depression in addition to diagnosis of a serious neurological condition. Stigma could often make clinicians reluctant to recognise or label the patient with depression. As a consequence, patients, carers and clinicians may be inclined to see the emotional problems as an inevitable and understandable emotional reaction to the neurological condition, rather than a condition that merits recognition and treatment. Evidence suggests that a dichotomy between seeing depression in neurological conditions as an emotional reaction or a biological process is artificial and unhelpful.
Whatever the cause of under-recognition, the impact of depression is significant with effects on patients and carers and long-term consequences on outcomes and costs. Given the frequency and significance of the problem, innovative brief screening methods may need to be routinely employed.5 There is evidence to suggest that relatively easy-to-administer instruments may have a good sensitivity and specificity to screen for depression.6 There is a need to further develop and evaluate briefer self administered scales that are specific to neurological conditions and are not cumbersome to score or interpret. Routine screening will increase the patient's and clinician's focus on this important problem and make neurologists more confident in diagnosing it.
Who should treat depression in neurological patients once it is diagnosed? Arguments have been made that neurologists should treat depression, too, in their patients and only refer patients who are refractory or have more complex presentations to neuropsychiatrists.7 General practitioners who treat the majority of depression in primary care could also take some of this responsibility. Given the number of such patients and current resources, it would be unrealistic to expect neuropsychiatrists or general psychiatrists to see all of these individuals.
The Price et al2 review summarises currently available evidence from the literature that includes 20 RCTs studying treatment of depression in a wide range of common neurological disorders such as stroke, Parkinson's disease, multiple sclerosis, brain injury and epilepsy. They find that the NNT for treating depression is 7 at 6–8 weeks and 4 after 9–18 weeks of randomisation. The trials reviewed indicated an advantage of treatment over placebo across antidepressant groups, with effect sizes a little higher for tri-cyclic antidepressants. This has to be balanced against their potential for toxicity, especially in an older, frailer population.
Evidence so far suggests that antidepressants are effective in treating depression in neurological settings. Hence, the neurologist should have a low threshold for diagnosing depression and should either initiate first-line antidepressant treatment themself or suggest the general practitioner instigate it. Neurologists may find it helpful to familiarise themselves with one antidepressant from each group. It may be helpful in situations such as epilepsy that they reassure GPs that reducing the seizure threshold is not a significant problem associated with commonly used first-line antidepressants such as selective serotonin reuptake inhibitors in therapeutic doses.
Clearly, there is an urgent need for more methodologically robust RCTs conducted for a longer duration with a long-term follow-up. It is worrying that treatment of depression in neurological disorders remains an under-researched area. Particularly functional outcome measures and quality-of-life measures need to be incorporated into such studies in the future. More studies will also be required to look into treatment of depression associated with various common neurological disorders to establish any differences based on neurological disorders.
Diagnosis and treatment of depression in a neurological condition will always be based on specific underlying factors of that condition rather than the basic fact of association of depression with a neurological disorder. While more robust evidence accumulates with time, there are indications at present that antidepressants work in these patients. Given the high human and material cost of untreated depression in neurological disorders, systematic approaches to identification and treatment of depression will have to become a core part of neurological services. Ready availability of neuropsychiatric support could foster this process.
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