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National Collaborating Centre for Mental Health (UK). Depression in Adults with a Chronic Physical Health Problem: Treatment and Management. Leicester (UK): British Psychological Society (UK); 2010. (NICE Clinical Guidelines, No. 91.)
Depression in Adults with a Chronic Physical Health Problem: Treatment and Management.
Show detailsBACKGROUND
This appendix sets out an approach to the classification of depression that was used in the development of this guideline and the depression guideline update (NCCMH, 2010) (including the analysis of the evidence and the development of recommendations) and will be of value in routine clinical use.
Depression is a heterogeneous disorder in which a number of underlying presentations may share a common phenomenology but have different aetiologies. Despite considerable work on the aetiology of depression including neurobiological, genetic and psychological studies, no reliable classificatory system has emerged that links either to the underlying aetiology or has proven strongly predictive of response to treatment. A number of classification systems/subgroupings have been used, including reactive and endogenous depression, melancholia, atypical depression, depression with a seasonal pattern/seasonal affective disorder and dysthymia. These have been based on varying combinations of the nature, number, severity, pattern and duration of symptoms, and in some cases the assumed aetiology. Over time pragmatic definitions have emerged, enshrined in the current two major classification systems, DSM–IV (APA, 2000a) and ICD–10 (WHO, 1992). These have defined a threshold of severity of clinical significance with further classification in terms of severity (for example, mild, moderate or severe as adopted in DSM–IV with regard to major depressive disorder), duration and course of the disorder (for example, recurrent, presence of residual symptoms) and subtype based on symptom profile (for example, melancholic, atypical). Other aspects of depression such as response to treatment (for example, treatment resistant, refractory) and aetiology (for example, preceding life events) do not feature specifically in the classifications and lack accepted definitions, although are used in clinical practice. The classification has some use in describing likely outcome and course (Khan et al., 1991; Barrett et al., 2001; Sullivan et al., 2003; Blom et al., 2007; Jackson et al., 2007; Conradi et al., 2008; Holma et al., 2008; Van et al., 2008) although social support, social impairment or personality factors also need to be taken into account. Lower severity and duration of a depressive episode predicts, to some extent, a greater likelihood of spontaneous or earlier and eventual improvement whereas greater severity, chronicity and number of previous episodes predict a higher chance of subsequent relapse.
The lack of a highly reliable or valid classificatory system has significant and practical clinical consequences, particularly in primary care where the full range of depression presents. A major concern is whether depression should be classified using dimensions or categories. Categories help distinguish cases from non-cases, whilst dimensions help identify severe disorder from mild (Cole et al., 2008). Clinicians are often required to make a categorical decisions – for example to treat with antidepressants or not, to refer for further interventions or not- and consequently there can be pressure to interpret data on a single dimension in a categorical way, for example, treat or not treat based solely on a symptom severity rating (for example, a PHQ-9 score alone). This conflicts with the recognised need to take multiple factors/dimensions into consideration within a consultation, including the patient's view on the cause of symptoms and acceptable treatment, and in this guideline and the depression guideline update a major challenge has been to provide a useful categorisation that adequately captures the complexity.
CLASSIFICATION OF DEPRESSION AND NICE GUIDANCE
The approach adopted in the first NICE depression guideline (NICE, 2004a; NCCMH, 2004) was based on ICD–10 and rested on a dimensional approach based on a symptom count further elaborated by taking into account the presence of social role impairment and the duration of both symptoms and social impairment. The subsequent categorisation of depression into mild, moderate and severe has led to a number of concerns in practice. First, this classification appears to have often been implemented with an emphasis on a symptom count alone with other important factors such as duration and social impairment ignored, although it should be noted that in general there is a relationship between the number of symptoms and severity of functional impairment (Faravelli et al., 1996). Second, it implies that the different symptoms experienced are equivalent, although, in fact, symptom patterns may be important. Third, it does not take into account illness duration and course. This tendency may be exacerbated by the use of measures such as the Patient Health Questionnaire (PHQ-9; Kroenke et al., 2001) or Hospital Anxiety and Depression Scale (HADS; Zigmond & Snaith, 1983) under the Quality and Outcomes Framework (Department of Health, 2004).
A drawback inherent in using ICD–10 depression criteria is that most of the treatment research on which the guidelines have to be based uses DSM–IV or previous, essentially similar, versions of DSM (DSM–III, and DSM–III–R) criteria. As discussed below, the criteria are similar but not identical, and this has particular relevance for the ‘threshold’ of the diagnosis of clinically significant depressive episode and therefore what are considered subthreshold or subthreshold depressive symptoms.
DIAGNOSIS OF A DEPRESSIVE/MAJOR DEPRESSIVE EPISODE
The criteria for diagnosing depressive episodes in ICD–10 and DSM–IV overlap considerably but have some differences of emphasis. In ICD–10 the patient must have two of the first three symptoms (depressed mood, loss of interest in everyday activities, reduction in energy) plus at least two of the remaining seven symptoms; while in DSM–IV the patient must have five or more out of nine symptoms with at least one from the first two (depressed mood and loss of interest). Both diagnostic systems require symptoms to have been present for at least 2 weeks to make a diagnosis (but can be shorter in ICD–10 if symptoms are unusually severe or of rapid onset). In both ICD–10 and DSM–IV the symptoms must result in impairment of functioning that increases with the episode severity. Table 69 compares the symptoms required in ICD–10 and DSM–IV.
DETERMINING SEVERITY OF A DEPRESSIVE/MAJOR DEPRESSIVE EPISODE
Both ICD–10 and DSM–IV classify clinically important depressive episodes as mild, moderate and severe based on the number, type and severity of symptoms present and degree of functional impairment. Table 70 shows the number of symptoms required by each diagnostic system, which are less specific than DSM–IV. The prescriptive symptom counting approach of ICD–10 tends to lend itself to using symptom counting alone to determine severity.
As ICD–10 requires only four symptoms for a diagnosis of a mild depressive episode, it can identify more people as having a depressive episode compared with a DSM–IV major depressive episode. One study in primary care in Europe identified two to three times more people as depressed using ICD–10 criteria compared with DSM–IV (11.3% versus 4.2%; Wittchen et al., 2001a). However another study in Australia (Andrews et al., 2008) found similar rates using the two criteria (6.8% versus 6.3%) but slightly different populations were identified (83% concordance), which appears to be related to the need for only one of two core symptoms for DSM–IV but two out of three for ICD–10. These studies emphasise that, although similar, the two systems are not identical and that this is particularly apparent at the threshold taken to indicate clinical importance.
DIAGNOSIS OF MINOR DEPRESSIVE DISORDER
Given how common milder forms of depression are, and the problems inherent in defining a ‘threshold’ of clinical importance because of the diagnostic system differences and the lack of any natural discontinuity identifying a critical threshold (Andrews et al., 2008), the guideline update, and by extension this guideline, has broadened its scope to include depression that is ‘subthreshold’, that is, does not meet the full criteria for a depressive/major depressive episode. A further reason is that subthreshold depression has been increasingly recognised as causing considerable morbidity and human and economic costs, is more common in those with a history of major depression and is a risk factor for future major depression (Rowe & Rapaport, 2006).
There is no accepted classification for this in the current diagnostic systems with the closest being minor depression, a research diagnosis in DSM–IV. At least two but less than five symptoms are required, of which one must be depressed mood or diminished interest. This includes ICD–10 depressive episode with four symptoms and, given the practical difficulty and inherent uncertainty in deciding thresholds for significant symptom severity and disability, there is no natural discontinuity between minor depression and mild major depression in routine clinical practice. There is, however, a danger of ‘medicalising’ distress by adopting minor depression as a discrete diagnosis, which would inevitably broaden the concept of depression. For this guideline and the depression guideline update, the GDGs used the term ‘subthreshold depressive symptoms’ to avoid this problem while providing a way of describing this part of the depressive spectrum.
Both DSM–IV and ICD–10 do have the category of dysthymia, which consists of depressive symptoms which are subthreshold for major depression but which persist (by definition for more than 2 years). There appears to be no empirical evidence that dysthymia is distinct from minor depression apart from duration of symptoms.
ICD–10 has a category of mixed anxiety and depression, which is less clearly defined than minor depression, and is largely a diagnosis of exclusion in those with anxiety and depressive symptoms subthreshold for specific disorders. Not unexpectedly it appears to be a heterogeneous category with a lack of diagnostic stability over time (Barkow et al., 2004; Wittchen et al., 2001b). For this reason it has not been included in this guideline.
DURATION
The duration of a depressive episode can vary considerably between individuals. The average course of an untreated depressive episode is between 6 and 8 months with much of the improvement occurring in the first 3 months, and 80% recovered by 1 year (Coryell et al., 1994). There is evidence to suggest that patients who do not seek treatment for their depression may recover more quickly than those who seek but do not receive treatment (Posternak et al., 2006). There is also some evidence to suggest that people who do not seek help have a shorter mean duration of depressive episode (Posternak et al., 2006).
Traditionally the minimum duration of persistent symptoms for major depression is 2 weeks and for chronic depression (or dysthymia) 2 years. These conventional definitions have been adopted in the absence of good evidence as there is only a modest empirical base for the minimum duration (for example, Angst & Merikangas, 2001) and none that we could find for the ‘cut-off’ between acute and chronic depression. As with severity, duration is better thought of as a dimension with a decreased likelihood of remission with increasing chronicity over a given time frame (Van et al., 2008). The conventional criteria are therefore better viewed as guides rather than cut-offs. It is likely that that the minimum duration after which therapy provides more benefit than occurs by spontaneous improvement is somewhat longer than 2 weeks (possibly 2 to 3 months, Posternak et al., 2006), but this has never been tested empirically. By 2 years it does appear that outcome is poorer, supporting consideration of chronicity in describing the disorder; nevertheless the point at which acute becomes chronic is not clear, and indeed may not be a meaningful question. There is some evidence that outcome is poorer after about 1 year (for example, Khan et al., 1991). However, there seems little to be gained by redefining duration for the guidelines as long as it is recognised that the conventional definitions are merely signposts to include consideration of duration in relation to outcome and need for treatment.
COURSE OF DEPRESSION
An influential model of the course of major depression proposes that the onset of an episode of depression consists of a worsening of symptoms in a continuum going from depressive symptoms through to major depression. Phases of improvement with treatment consist of response (significant improvement) to remission (absence of depressive symptoms) which, if stable for 4 to 6 months, results in (symptomatic) recovery, meaning that the episode is over (Frank et al., 1991). It is important to distinguish this use of recovery from more recent concepts related to quality and meaning of life in spite of continued symptoms. After recovery a further episode of depression is viewed as a recurrence to distinguish it from a relapse of the same episode. There has been no consensus as to how long a period of remission should be in order to be able to declare recovery; different definitions result in different definitions of episode length and time to full or subthreshold depressive recurrence (Furukawa et al., 2008). Therefore, in practice it can be difficult to distinguish between relapse and recurrence, particularly when people have mild residual symptoms. Follow-up studies of people with depression have shown that, overall, more time is spent with subthreshold depressive symptoms than major depression and there is a variable individual pattern ranging from persisting chronic major depression, through significant but not full improvement (partial remission), to full remission and recovery (Judd et al., 1998). DSM–IV defines full remission when there has been an absence of symptoms for at least 2 months. For partial remission, full criteria for a major depressive episode are no longer met, or there are no substantial symptoms but 2 months have not yet passed. DSM–IV specifies ‘with full inter-episode recovery’ if full remission is attained between the two most recent depressive episodes and ‘without full inter-episode recovery’ if full remission is not attained. In DSM–IV, therefore, separate episodes are distinguished by at least 2 months of not meeting major depression criteria, which is in contrast to the more stringent ICD–10 requirements of 2 months without any significant symptoms. There is therefore some ambiguity as to whether full remission is required to define separate episodes.
Nevertheless, the number of episodes and degree of symptom resolution have important implications for considering the course of an individual patient's depressive disorder. The risk of a further episode of major depression within a given time frame is greater with an increasing number of previous episodes (Kessing & Andersen, 2005; Solomon et al., 2000) and also if there has not been full remission/symptomatic recovery (Dombrovski et al., 2007; Kanai et al., 2003; Paykel et al., 1995). If someone presents with minor depressive symptoms it is therefore crucial to determine whether or not this directly follows an episode of major depression.
DEPRESSION SUBTYPES
Different symptom profiles have been described and are included in the classification systems. In DSM–IV, severe major depression can be without or with psychosis (psychotic depression) and there are specifiers that include melancholia, atypical features, catatonia, seasonal pattern (seasonal affective disorder) and post-partum onset. ICD–10 also provides specifiers for psychotic and somatic symptoms, the latter similar to DSM–IV melancholia. However, these subtypes do not form distinct categories (for example, Kendell, 1968; Angst et al., 2007) and they add a further complexity to the diagnosis of depression. The GDGs judged that these specifiers were best considered where appropriate after the diagnosis of a depressive disorder is made and they are not discussed in detail here. Some specifiers, particularly psychosis and seasonal pattern depression, have potential treatment implications and are considered in the depression guideline update where evidence is available.
CLASSIFICATION OF DEPRESSION IN THIS GUIDELINE AND THE DEPRESSION GUIDELINE UPDATE
The depression classification system adopted for this guideline and the depression guideline update had to meet a number of criteria, notably the use of:
- a system that reflects the non-categorical, multidimensional nature of depression
- a system that makes best use of the available evidence on both efficacy and effectiveness
- a system that could be distilled for practical day-to-day use in healthcare settings without potentially harmful over-simplification or distortion
- terms that can be easily understood and are not open to misinterpretation by a wide range of healthcare staff and service users
- a system that would facilitate the generation of clinical recommendations.
These criteria led the GDGs to adopt a classificatory system for depression based on DSM–IV criteria. When assessing an individual it is important to assess three dimensions to diagnose a depressive disorder – (a) severity (symptomatology and social impairment), (b) duration, and (c) course – as linked, but separate, factors (see below). In addition, there was recognition that a single dimension of severity was insufficient to fully capture its multidimensional nature.
As discussed above, the following depressive symptoms require assessment to determine the presence of major depression. The symptoms need to be experienced to a sufficient degree of severity and persistence to be counted as definitely present. At least one core symptom is required; both core symptoms would be expected in moderate and severe major depression.
Core symptoms of depression
- Depressed mood most of the day, nearly every day.
- Markedly diminished interest or pleasure in all, or almost all, activities most of the day, nearly every day.
Somatic symptoms
- 3.
Significant weight loss when not dieting or weight gain (for example, a change of more than 5% of body weight in a month), or decrease or increase in appetite nearly every day.
- 4.
Insomnia or hypersomnia nearly every day.
- 5.
Psychomotor agitation or retardation nearly every day (observable by others, not merely subjective feelings of restlessness or being slowed down).
- 6.
Fatigue or loss of energy nearly every day.
Other symptoms
- 7.
Feelings of worthlessness or excessive or inappropriate guilt (which may be delusional) nearly every day (not merely self-reproach or guilt about being sick).
- 8.
Diminished ability to think or concentrate, or indecisiveness, nearly every day.
- 9.
Recurrent thoughts of death (not just fear of dying), recurrent suicidal ideation without a specific plan, or a suicide attempt or a specific plan for committing suicide.
The symptoms are not due to the direct physiological effects of a substance (for example, a drug of misuse or a medication) or a general medical condition (for example, hypothyroidism) or better accounted for by bereavement.
There is evidence that doctors have difficulty in remembering the nine DSM–IV depressive symptoms (Krupinski & Tiller, 2001; Rapp & Davis, 1989), which has important implications for the application of these criteria. In addition, there is the need to be able to consistently diagnose depression in patients where physical symptoms may be due to medical illness. Zimmerman and colleagues (2006) and Andrews and colleagues (2008) have demonstrated that, compared with the diagnosis using the full DSM–IV criteria, there is a high agreement (94 to 97%) and good sensitivity (93%) and specificity (95 to 98%) when a reduced list (excluding the four somatic symptoms) is used with a requirement for three out of the remaining five symptoms.
It is therefore possible to use an abridged list, first asking about the two core symptoms of depression:
- persistent depressed mood
- markedly diminished interest or pleasure.
Then if either or both are present, going on to ask about:
- feelings of worthlessness or guilt
- impaired concentration
- recurrent thoughts of death or suicide.
Three or more symptoms indicate a very high probability of major depression. This does not, however, replace the need to go on to assess somatic symptoms as an aid to determining severity and to help judge subsequent response to treatment. This limits the usefulness of the abridged list in practice and it may be most useful when there are confounding somatic symptoms due to physical illness.
Severity
While recognising that severity is not a unitary dimension, practically it is useful to make a judgement of severity consisting, at least, of number of symptoms, severity of individual symptoms and functional impairment. This leads to a classification of depression into the following severity groupings based on DSM–IV criteria, which should be viewed as exemplars not discrete categories. In the guidelines the term depression refers to major depression:
- subthreshold depressive symptoms: fewer than five symptoms of depression
- mild depression: few, if any, symptoms in excess of the five required to make the diagnosis, and the symptoms result in only minor functional impairment
- moderate depression: symptoms or functional impairment are between ‘mild’ and ‘severe’
- severe depression: most symptoms, and the symptoms markedly interfere with functioning; can occur with or without psychotic symptoms.
Symptom severity and degree of functional impairment correlate highly (for example, Zimmerman et al., 2008), but in individual cases this may not be the case and some mildly symptomatic individuals may have marked functional impairment while some people who are severely symptomatic may, at least for a time, maintain good function, employment and so on.
Duration
By convention the duration of persistent symptoms is required to be at least 2 weeks and, once they have persisted for 2 years or more, they are called chronic in the case of major depression or dysthymia in the case of subthreshold depressive symptoms. While the specific values may not be particularly helpful, there are insufficient empirical data to change these:
- Acute – meeting one of the severity criteria for a minimum of 2 weeks and not longer than 2 years.
- Chronic – meeting one of the severity criteria for longer than 2 years.
Given that the cut-off of 2 years is arbitrary, it is best in practice to consider the specific duration and degree of persistence of symptoms for an individual in the context of the severity and course of the disorder.
Course
This was not explicitly considered as a classificatory issue in the first NICE depression guideline but it has important treatment implications, particularly for the likelihood of relapse/recurrence.
- Number of lifetime depressive episodes and the interval between recent episodes: the number varies from a single/first episode to increasingly frequent recurrences. At least 2 months of full or partial remission is required to distinguish episodes.
- Stage of episode: this refers to where an individual is in the course of their depression. In an episode it is useful to determine if the depression is worsening, static or improving and whether subthreshold depressive symptoms may reflect partial remission from prior major depression.
Conventionally, classification has distinguished between a single episode and two or more episodes (recurrent depression) irrespective of how long there has been between episodes and how many recurrences have occurred. However, someone who has had two episodes separated by decades has a different clinical course from someone with three episodes in a few years; therefore, noting the number of episodes and their recent pattern is important. There is uncertainty about the duration and extent of the recovery that is required to distinguish between different episodes of depression and a fluctuating course of a single episode. In practice this is less important than recognising the risk of persistent symptoms and of major depressive relapse/recurrence.
CLASSIFICATION IN RELATION TO DEPRESSION RATING SCALES AND QUESTIONNAIRES
Depression rating scales and questionnaires give ranges that are proposed to describe different severities of depression. Some of these were described in Appendix 13 of the first NICE depression guideline. In reconsidering this for this guideline and the guideline update, it quickly became apparent not only that there is no consensus for the proposed ranges but also that the ranges in different rating scales and questionnaires do not correspond with each other. In addition, there a variable degree of correlation between different scales, which indicates that the they do not measure precisely the same aspects of depression. When these factors are added to the need to consider more than symptoms in determining severity, and more than severity in considering diagnosis, the GDG was concerned not to perpetuate a spurious precision in relating scores in depression rating scales and questionnaires to the diagnosis or severity of depression, which must in the end be a clinical judgement.
Nevertheless it is necessary to try and translate trial evidence (which may only provide rating scales or questionnaire scores) into a meaningful clinical context as well as relating this guideline and the depression guideline update to the first NICE guideline which used the APA (2000b) cut-offs. The change to DSM–IV-based diagnosis and the inclusion of minor depression (subthreshold depressive symptoms) in the update means that the descriptors of ranges previously given are no longer tenable. Table 71 gives the descriptors and ranges used in this guideline update, with the important caveat that these must not be taken as clear cut-offs or a short-cut to classify people with depression.
IMPLICATIONS OF THE PROPOSED CLASSIFICATION
An important implication is that symptom counts alone (for example, using the PHQ-9) should not be used to determine the presence or absence of a depressive disorder although this is an important part of the assessment. The score on a rating scale or questionnaire can contribute to the assessment of depression and rating scales are also useful to monitor treatment progress.
Another very important point to emphasise is that the making of a diagnosis of depression does not automatically imply a specific treatment. Making and agreeing a diagnosis of depression is a starting point in considering the most appropriate way of helping that individual in their particular circumstances. The evidence base for treatments considered in this guideline are based primarily on RCTs in which standardised criteria have been used to determine entry into the trial. Patients seen clinically are rarely assessed using standardised criteria reinforcing the need to be circumspect about an over-rigid extrapolation from RCTs to clinical practice.
Diagnosis using severity, duration and course (see above) necessarily only provides a partial description of the individual experience of depression. People with depression vary in the pattern of symptoms they experience, their family history, personalities, premorbid difficulties (for example, sexual abuse), psychological mindedness and current relational and social problems – all of which may significantly affect outcomes. It is also common for people with depression to have a comorbid psychiatric diagnosis, such as anxiety, social phobia, panic and various personality disorders (Brown et al., 2001), and physical comorbidity, or for the depression to occur in the context of bipolar disorder (not considered in this guideline). Gender and socioeconomic factors account for large variations in the population rates of depression, and few studies of pharmacological, psychological and other treatments for depression control for or examine these variations. This emphasises that choice of treatment is a complex process and involves negotiation and discussion with patients. Given the current limited knowledge about what factors are associated with better antidepressant or psychotherapy response, most decisions will rely upon clinical judgement and patient preference until there is further research evidence. Trials of treatment in unclear cases may be warranted but the uncertainty needs to be discussed with the patient and benefits from treatment carefully monitored.
- BACKGROUND
- CLASSIFICATION OF DEPRESSION AND NICE GUIDANCE
- DIAGNOSIS OF A DEPRESSIVE/MAJOR DEPRESSIVE EPISODE
- DETERMINING SEVERITY OF A DEPRESSIVE/MAJOR DEPRESSIVE EPISODE
- DIAGNOSIS OF MINOR DEPRESSIVE DISORDER
- DURATION
- COURSE OF DEPRESSION
- DEPRESSION SUBTYPES
- CLASSIFICATION OF DEPRESSION IN THIS GUIDELINE AND THE DEPRESSION GUIDELINE UPDATE
- CLASSIFICATION IN RELATION TO DEPRESSION RATING SCALES AND QUESTIONNAIRES
- IMPLICATIONS OF THE PROPOSED CLASSIFICATION
- The classification of depression and depression rating scales/questionnaires - D...The classification of depression and depression rating scales/questionnaires - Depression in Adults with a Chronic Physical Health Problem
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