Depression Defined
There are different forms of depression and depression can noticeable itself in different grades of acuteness. On the whole, a depressive feeling is a feeling that is generally experienced by practically everyone at some time in life. The depressive feeling can be a normal emotional reaction e.g., in unusual normative predicaments during an individual’s life-cycle (Stahl, 2001). ‘Depressive feeling can also manifest itself as a special symptom in different mental or somatic disorders’ (Aalto-Setälä, 2002). As ill health, depression is a socially devastating syndrome including clusters of symptoms, only one symptom of which is the irregularity of frame of mind (Stahl, 2001). In depressive disorders, one has lost the sense of control of one’s frame of mind and affects: Patients suffering from depressive disorders might experience loss of energy and interest; they have feelings of guilt/worthlessness and difficulties in concentrating. They also might have a loss of hunger, sleeplessness or hypersomnia, and normally experience thoughts of death or suicide/suicidal behavior. ‘In the most severe form of depression, i.e., major depression with psychotic features, patients also have delusions or hallucinations’ (Kaplan et al, 1994).
All over the history of psychiatry, there have been many different classifications of depression. As regards diagnosing depression, modern epidemiological surveys nowadays generally conceptualize depression as a diagnosis, based on the standard of diagnostic systems such as DSM-IV diagnostic classification (American Psychiatric Association 1994) or ICD-10 (International Classification of Disorders) (World Health Organization 1992) as studied by Aalto-Setälä (2002). In the DSM-IV, for example, the following depression diagnoses are given viz. Major depressive disorder, dysthymia, adjustment disorder with depressed mood, and depressive disorder not otherwise specified (American Psychiatric Association 1994). As well as structured or semi-structured diagnostic instruments, there are a number of rating scales designed to determine depressive symptoms, the value of which is well established in obtaining estimates of symptom prevalence in the population and for testing purposes (Aalto-Setälä 2002).
Introduction
It is an illness that involves the body, mood, and thoughts, that affects the way a person eats and sleeps, the way one feels about oneself, and the way one thinks about things. A depressive disorder is not the same as a passing blue mood. It is not a sign of personal weakness or a condition that can be wished away. People with a depressive disease cannot merely “pull themselves together” and get better. Without treatment, symptoms can last for weeks, months, or years. Proper treatment, nevertheless, can help most people with depression.
The signs and symptoms of depression include loss of interest in activities that were once interesting or enjoyable, loss of appetite (anorexia) with weight loss or overeating with weight gain; loss of emotional expression; a persistently sad, anxious, or empty mood; feelings of despair, cynicism, guilt, worthlessness, or helplessness; social withdrawal; unusual fatigue, low energy level, a feeling of being slowed down; sleep disturbance with sleeplessness, early-morning awakening, or oversleeping; trouble concentrating, remembering, or making decisions; abnormal restiveness or bad temper; persistent physical problems such as headaches, digestive disorders, or chronic pain that do not respond to treatment; thoughts of death or suicide or suicide attempts. Alcohol or drug abuse may be signs of depression.
The principal types of depression are major depression, dysthymia, and bipolar disease (also called manic-depressive disease). Major depression causes a combination of symptoms that interfere with the ability to work, study, sleep, eat, and enjoy once pleasurable activities. Such a disabling occurrence of depression may take place only once however more commonly happens several times in a lifetime.
Dysthymia is a less severe type of depression with long-term chronic symptoms that do not disable but keep one from functioning well or from feeling good. Many people with dysthymia also experience major depressive incidents at some time in their lives.
Bipolar disorder (manic-depressive illness) is characterized by cycling mood changes: severe highs (mania) and lows (depression). Sometimes the mood switches are remarkable and rapid, however more often they are steady. When in the depressed phase of the cycle, one can have any or all of the symptoms of a depressive disorder. When in the manic cycle, one may be overactive, over-talkative, and have excess energy. Mania often affects thinking, intelligence, and social behavior in ways that cause acute problems and humiliation. For instance, the individual in a manic phase may feel delighted, full of grand schemes that might range from imprudent business decisions to idealistic sprees. Mania left untreated, may aggravate a psychotic state. Bipolar disorder is not virtually as common as other forms of depressive disorders.
The signs and symptoms of mania include abnormal or excessive excitement; noticeably increased level of energy; less need for sleep; ostentatious ideas; racing thoughts and increased talking; poor intelligence; and wrong social behavior.
Clinical depression is yet widely misinterpreted. The current attitude is “Keep a stiff upper lip, have a drink, maybe it will go away.” About 12% of men and up to 25% of women suffer from depression during their lifetimes. At the same time as more women attempt suicide, men are more likely to be successful.
Classification of Depression
The classification of depression types is a contentious topic that has caused much discussion between psychiatrists. This suggests that if there are different types of depression then they may have different causes and outcomes, and respond to different treatments.
Controversies arise since diagnoses are simply based on the occurrence of certain, arbitrarily defined, symptoms. There is still no diagnostic test for depression, such as a blood test or scan, which is able to confirm whether somebody has the illness. This lack of an objective ‘gold standard’ diagnosis means that doctors do not know for certain whether the clusters of symptoms they use for diagnosis are applicable, or even if they are dealing with one or more diseases that have the same central symptom of low mood.
Another difficulty is that different psychiatrists earlier used different measures to diagnose depression. Much of the resulting confusion has been reduced by the initiation of internationally recognized sets of diagnostic criteria such as the Diagnostic and Statistical Manual (DSM) and the International Classification of Disease (ICD).
These standards have led to greater uniformity of approach to the diagnosis and classification of depressive illnesses. Nevertheless, the criteria and classes of depression are regularly reorganized with each new version of DSM and ICD, and there continue to be differences in opinion between some psychiatrists.
Over the years some authorities have tried to subdivide ‘straightforward’ depression on the strength of the cause of the illness and the type of symptoms experienced. These include:
- Endogenous versus reactive depression.
- Psychotic versus neurotic depression.
- Major versus minor depression.
Endogenous vs. Reactive Depression
The endogenous versus reactive classification was based on ideas regarding the cause of the depressive illness.
Endogenous Depression
- ‘Endogenous’ (occurs from within) implied there was no noticeable cause for the depression.
- It was thought that this type of depression was more likely to be passed on to children as a result of a larger genetic component than reactive depression.
- This form of depression was thought characterized by a high proportion of biological symptoms.
- Some authorities thought this form of depression was most likely to respond to antidepressant treatments.
Reactive Depression
- ‘Reactive’ implied that the depression resulted from some stress happening in the sufferer’s life.
- The risk of this type of depression going on was believed to have more to do with the rigorousness of life stresses than inherited factors.
- Symptoms are thought to be characterized by worry and anxiety, with problems getting to sleep rather than waking early in the morning.
- It was initially argued that patients with reactive depression were less likely to respond to antidepressants.
Psychotic vs. Neurotic Depression
This differentiation depends on the principle that patients with depression could be divided into two groups on account of their symptoms. This classification almost exactly matched the endogenous vs. reactive classification, with the ‘psychotic’ group being like the ‘endogenous’ group.
The use of the term ‘psychotic’ is extremely confusing since it usually refers to the presence of particular symptoms that were not essentially present in ‘psychotic depression’ as defined in this classification.
Major vs. Minor Depression
This particularly inopportune use of terminology also followed the ‘endogenous versus reactive’ classification. The use of the term ‘minor’ is not only disparaging, but it also encouraged a lack of treatment of patients with so-called ‘minor depression’. The term ‘major’ is also confusing since it does not essentially imply ‘severe’ illness.
Currently accepted Types of Depression
Primary vs. Secondary Depression
This distinction is founded on the proposed cause of the depressive illness in an individual.
- Primary: the depression is not in consequence of any other medical or psychological cause.
- Secondary: depression has been caused by a medical condition for instance a disorder of the thyroid gland or psychiatric illness.
There is little evidence that these ‘types’ of depression are different. However, this classification helps to draw attention to any possible underlying causes of depression. These causes then need treating in their own right if the depression is to improve.
Unipolar vs. Bipolar Depression
This classification is based on the course of the illness that an individual experiences.
- If a patient has only ever had incidents of depression, they are described as having a unipolar affective disorder.
- If a patient has had at least one occurrence of elevated mood (mania) in addition to incidents of depression, they are described as suffering from a bipolar affective disorder (manic depression). A few people only suffer occurrences of mania; they are also referred to as suffering from a bipolar affective disorder.
The unipolar versus bipolar distinction is important since many differences between the two illnesses exist.
- Both disorders can be inherited, however, this is more likely to be the case with bipolar disorder. The children of unipolar disorder parents have an increased risk of this type of depression. Nevertheless, the children of people with bipolar disorder have an increased risk of both, which suggests the two disorders are related.
- Bipolar disorder tends to begin earlier in life than unipolar disorder, often starting in the early 20s rather than in the 30 to 40 year age range.
- Patients with bipolar disorder tend to have more regular incidents of illness than patients with unipolar depression, though these occurrences tend to be shorter.
- Bipolar disorder can sometimes be made worse by antidepressants, which can sudden a manic (elevated mood) episode and/or lead to more frequent episodes of illness. Mood stabilizers such as lithium and some anticonvulsants are the basis of treatment for bipolar disorder patients.
Depressive illness vs. Depressive Symptoms
Everyone can have a low mood from time to time, although this is different from suffering from a depressive illness. A depressive illness is identified when a person has several depressive symptoms constantly over a couple of weeks or more.
According to the diagnostic criteria of DSM and ICD, a depressive illness is present if a person is suffering from a definite number of specific symptoms. However, the question arises as to what about a person who has several depressive symptoms, although not enough to meet the diagnostic criteria for a depressive illness. There are however many possibilities:
- The person may not be experiencing a depressive illness.
- The person may be suffering from a depressive illness that has a somewhat different pattern of symptoms that does not fit with the arbitrarily defined list of symptoms defined in the criteria.
- The person may be suffering from a milder form of depressive illness.
- The person may be in the early stages of a depressive illness and in due course develop more symptoms and thus meets the diagnostic criteria.
These possibilities affect the way that a person with depressive symptoms, although not meeting the criteria for a depressive illness, gets treated:
- If symptoms have been present for less than two weeks, beyond giving some general support and possibly counseling, antidepressants tend not to be used.
- Nevertheless, if the symptoms are severe and have been present for more than two weeks, a doctor would be more likely to advise antidepressants.
- The progress of people with depressive symptoms should be checked, since they may go on to develop a developed depressive illness that will require treatment.
Dysthymia vs. Depressive illness
This distinction is founded on the severity and number of symptoms, and the period of the illness.
Dysthymia is defined by the presence of depressive symptoms for at least two years. A diagnosis of dysthymia rather than a depressive illness is made because:
- Either there are not enough symptoms present to meet the diagnostic criteria for a depressive illness.
- Or the symptoms are not present for the majority of the time, although may rise and fall for a few days at a time.
Dysthymia appears to react in a different way to treatment compared to depressive illnesses.
- There is less verification that psychotherapies work.
- Antidepressants may be of some help; however, can take months to start working. Therefore, a great deal of patience is called for on both the part of the patient and the doctor.
People with dysthymia are at increased risk of also developing a developed depressive illness on top of their constant depressive symptoms. This is sometimes called ‘double depression’, meaning dysthymia as well as a depressive illness. If this happens, then treatment for the depressive illness is particularly important to check a persistent full-size depressive illness developing.
Preventive Measures, Prognostic factors in Depression
In homes for the old, depressive and anxiety disorders are very common and have a large impact on the well-being and daily working of the residents. In 2002 over 90,000 of the nearly one million elderly persons for instance in the Netherlands aged 75 years or older, living in a residential home. Up to 30 percent of these residents develop symptoms of depression and anxiety, such as lack of interest and feelings of loneliness and despair. In about 30 to 35 percent of residents with symptoms of depression and anxiety, these symptoms ultimately develop into major depression and generalized anxiety disorder. These disorders are often associated with bad prospects and with excess mortality, disability, and handicap, and service utilization (Cuijpers, 2001; de Beurs et al, 1999; Katon et al, 2003; Schoevers et al, 2005). Treatment can lessen the illness burden in the population, however only to a moderate extent (Schoevers et al, 2006). Hence, prevention may be a remarkable choice.
Indicated prevention, in place of universal prevention or selective prevention, aims to oppose the commencement of development of a disorder in those who already have symptoms. Indicated prevention may be a successful approach in view of the fact that it targets high-risk persons who are identified as having nominal symptoms foreshadowing mental disorders. Risk factors for depression and anxiety disorders in the general population are known; a large naturalistic follow-up study among persons 55 years of age in the community showed that a set of six indicators explained 83% of the total prognostic variance. The prediction model includes symptoms of depression and/or anxiety disorder, functional limitations, a small network, female gender, low education, or suffering from recurring diseases (Smit et al 2006). These characteristics are very common among residents of homes for the elderly, which makes the population at high risk for depressive and anxiety disorders. Indicated prevention studies, in different target populations, have shown that several interventions are capable of reducing the occurrence of depression and anxiety disorder up to about 30% (Cuijpers et al, 2005). From a moral and communal viewpoint, indicated prevention is preferred to general prevention and selective prevention. Prevention activities may increase fear or apprehension in the target population; nevertheless, this is legitimated most for people who already suffer from symptoms and are known to have a high risk.
Even though caregivers in the homes know the impact of the problem, symptoms of depression and anxiety are hardly ever identified and labeled as such (Bagley et al, 2000; Eisses et al, 2005). A considerable part of residents of homes for the elderly suffers from physical co-morbidity. Symptoms of depression and anxiety disorder like indifference and tiredness may also be ascribed to physical illnesses (Katz et al, 1990). This makes that symptoms of anxiety and depression are often interpreted only as consequences of decline rather than problems that require intervention. Physical illness in the elderly is most of the time progressive and difficult to treat. Depressive and anxiety disorders, on the other hand, have more positive prospects for prevention and treatment (Cuijpers et al, 2005; Cuijpers & van Lammeren, 2001; Frazer et al, 2005). Besides, as the population is aging rapidly and the policy is to help independent living as much as possible, the level of psychological and physical frailty in homes for the elderly has been increasing rapidly.
Critical Analysis
Depression is among the most widespread psychiatric disorders and is the principal cause of disability in the United States, affecting more than 18 million Americans (National Institute of Mental Health, 2005).
Depression is a term that has both lay meanings and meaning as a psychiatric diagnosis. Periods of sadness or “feeling blue,” with feelings of loss and mourning, are a normal part of the human condition. Depressive symptoms can be a reaction to traumatic life events, such as illness or hospitalization. Patients may also be diagnosed with depression when they meet the condition for major depressive disorder. Consequently, ‘depression can be an affective experience, asymptomatic complaint, or a clinical syndrome’ (Rouchell, Pounds & Tierney, 2002). The margin between normal and abnormal symptoms is often indistinct and may be subjective. It is generally established by measure for symptom rigorousness, extent, and clinically important distress or injury and must be considered in the context of the patient’s personal situation (American Psychiatric Association, 2000; Gotlib & Hammen, 2002; Pasacreta, Minarik, & Nield-Anderson, 2000).
Generally documented as having a neurobiological basis, depression relates to other medical disease in four ways. It may be a cause or early sign of a medical condition. When depression takes place after the medical condition, it may be a pathophysiologic effect of the medical illness or a reaction to prescribed drugs or substances. Lastly, it may be a psychological reaction to the medical illness. ‘Depression and medical illness also can coexist but be etiologically unrelated’ (Rouchell et al., 2002).
Diagnostic terms for depression include major depressive occurrence or disorder, adjustment disorder with depressed mood, dysthymia or dysthymic disorder, mood disorder as a result of a general medical condition, and substance-induced mood disorder. Major depressive disorder (MDD) is distinguished by one or more major depressive episodes lasting at least 2 weeks and described by depressed mood or reduced interest or pleasure for most of the day almost every day. It is along with at least four out of nine depressive symptoms: depressed mood; reduced interest or happiness; changes in appetite or weight; sleeplessness or hypersomnia; psychomotor agitation or retardation; fatigue or loss of energy; feelings of worthlessness or unnecessary or inappropriate guilt; reduced ability to think or focus, or hesitancy; and persistent thoughts of death, recurrent suicidal ideation, suicide attempt, or definite plan for suicide. The period includes clinically important distress or impairment in social, occupational, or other important areas of functioning. The symptoms cannot be a result of the direct effects of a substance or a general medical condition (APA, 2000; Rouchell et al., 2002).
Minor depression is a term used in clinical practice in general hospital settings and in research. Minor depressive disorder is included in the current edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM) as a research diagnosis, meaning that there was inadequate confirmation or professional agreement to include it as an official diagnosis at the time of publication (APA, 2000). Minor depressive disorder refers to one or more periods of depressive symptoms lasting at least 2 weeks however involving fewer signs and less impairment than MDD.
Subsyndromal depression is the occurrence of symptoms that do not meet the criteria for a diagnosis and is of emergent interest in research and clinical practice. Kessler (2002) states that research using screening scales shows a high incidence of symptoms and a relatively low prevalence of the depressive disorder. This pattern suggests that many people have depressive symptoms that do not meet the criteria for a diagnosis of MDD.
Experimental & Theoretical Aspects
One of the most remarkable features of depression noted from early psychoanalytic formulations onwards is the persistent negativity of depressed patients’ thinking and affect. Of course, most investigators have assumed that depression enhances all forms of negative affect. Conceivably most conspicuously, cognitive theorists have developed a notion of depression in which negative moods and negative emotions are mutually supportive (Beck, 1967, 1976). In accordance with this view, depression can be conceptualized in terms of cognitive structures that harmfully misrepresent the processing of emotional stimuli. Notably, negative mood states strengthen these cognitive structures, increasing emotional responses when depressed persons come across a negative stimulus.
Despite the fact that the hypothesis that negative moods potentiate negative emotions in depressed individuals is a reasonable one, emotional reactivity to standardized negative emotion-eliciting stimuli has seldom been assessed in depressed persons. In a recent study, it was found that, compared with healthy controls, depressed individuals in fact showed less disparity reactivity to sad stimuli, and instead showed sadness in a stereotyped, context-insensitive fashion (Rottenberg, Kasch, Gross, & Gotlib, 2002). In addition, even when displaying a strong form of sadness i.e. tearful crying—depressed persons showed less emotional reactivity than healthy controls (Rottenberg, Gross, Wilhelm, Najmi, & Gotlib, 2002). In contradiction, then, the findings suggest that persistent sad moods in depression may slow down the generation of sad emotions. These findings confirm other clinical observations of emotional deadening in depression and raise the possibility that this disorder can be treated with techniques that improve patients’ emotional reactivity.
As well as clarifying the character of its main concepts, modern emotional science has also begun to elucidate the temporal course of affective processes as they clarify in due course. For instance, it has been shown that the course of emotional response can be usefully decomposed and studied in terms of its temporal constituents, such as rise time to peak or time to recovery (Davidson, 1998). Thus, besides excesses or deficiencies in the general magnitude of emotional responding, it seems very likely that dysfunctions of emotion will involve anomalies in one or more of these temporal parameters as well.
For example, recent empirical work advocates that changes in the offset of negative emotion may be especially important for understanding psychopathology (e.g., Siegle et al, 2002). One method that may play a role in negative emotion offset is parasympathetic tone, generally indexed by respiratory sinus arrhythmia (RSA), which refers to the changes in heart period that match with respiration. In previous work, RSA has been related to organismic flexibility and resiliency in the face of stressors. To test whether RSA tracks recovery from negative emotion, RSA fluctuations were measured that happened over the course of tearful crying incidents. Interestingly, healthy control participants who cried showed large increases in RSA that coincided with the resolution of their crying. On the other hand, depressed participants who cried did not show RSA rebound over this period, compatible with the idea that depression compromises emotion offset (Rottenberg, Wilhelm, Gross, & Gotlib, 2003).
Prevalence of Depression
As with atopic disorders (Galil, 2000), also depressive disorders (Galil, 2000) are illnesses of major public health value in many Western societies. As studied by Lehtinen and Joukamaa (1994), according to population surveys performed in many countries, the occurrence of clinically defined depression varies from 2.6% to 5.5% and from 6.0% to 11.8% in men and in women, respectively. Besides, the incidence of depressive symptoms is far more common between both genders when compared with depressive disorders, their occurrence ranging from 18% to 34% and from 10% to 19% for females and males, respectively. Therefore, both depressive symptoms and depressive disorders are among women about twice as common among men.
Etiological Factors of Depressive Disorders
Depression is recognized as a multifactorial disease by origin. Different biological, genetic, and psychosocial factors are known to be behind the psychopathology of depressive disorders (Kaplan et al, 1994).
Several lines of evidence that is family, twin, and adoption studies suggest that major depression is an ancestral disorder and that in the majority of the cases in which a trend of family preponderance is noticed; it is caused by genetic factors (Kendler & Aggen, 2001). It has been estimated that among first-degree relatives of persons suffering from depressive disorders the incidence of unipolar depression varies from 6.4% up to even 29.4%. As well, in a large twin study, genetic factors have recently been shown to play a greater role in the etiology of major depression among females than in males (Kendler et al. 2001a). The notion of psychosocial/environmental factors behind the etiology of depression is based on the fact that the start of depression is often preceded by traumatic life events and/or crises of a person’s life cycle. The general understanding of the depressogenic effects of traumatic life events seems to be equal for both genders, even though the psychosocial stressors themselves, prior to major depression in adulthood, differ between genders (Kendler et al, 2001c).
Relationship between Atopic Disorders & Depression
As reviewed by Galil (2000), relationships between asthma and psychiatric symptoms were explained with the help of psychoanalytic theories earlier in the 20th century: it was, for instance, suggested that asthma was caused by an excessive dependence on the mother and that it was precipitated by traumatic separations. Ever since genetic factors behind both asthma and depression have become evident, these earlier psychoanalytic explanations have mostly been abandoned (Galil 2000).
Allergic Symptoms in Patients with Depression
There have been Higher than normal rates of IgE-mediated allergies reported in patients with depression (Nasr et al, 1981; Sugerman et al, 1982). Nasr et al. (1981) assessed the personal and family history of bronchial asthma and/or allergic rhinitis from 82 psychiatric patients. Psychiatric diagnoses were based upon the 3rd edition of the Research Diagnostic Criteria. A semi-structured interview was performed to investigate the correlation between physical and mental problems. The cases of intrinsic asthma were excluded from the analyses since they were not likely to be allergic in nature. A statistically significantly higher incidence of atopic disorders was found in emotional patients than in schizophrenic patients.
Sugerman et al (1982) compared IgG, IgA, IgM, IgE, and IgD antibodies in adult alcoholic, depressive, and schizophrenic patients with those of adult, healthy controls. Total above-mentioned and specific IgE antibodies were evaluated, using 12 inhalants and 21 food allergens. No statistically noteworthy differences were observed in the total immunoglobulin results between patients and controls. Nevertheless, major differences were found between the groups for allergen-specific-IgE with depressive patients giving the greatest number of positive test results.
Depression in patients with Atopic Disorders
Hashiro and Okumura (1997) studied anxiety (manifest anxiety scale, MAS), depression (self-rating depression scale, SDS), and psychosomatic symptoms (Cornell Medical Index, CMI) in 45 patients with atopic dermatitis and 34 normal controls. On the MAS, the atopic dermatitis group did not show any statistical difference from the normal controls. When compared with the controls, the SDS and the CMI produced statistically significantly higher scores in patients with atopic dermatitis. As regards SDS, 44.4% of the patients with atopic dermatitis had scores of 40 or more, the corresponding percentage being 29.4% in the normal controls. After classifying atopic patients in three degrees of severity the patients with moderate symptoms were more depressive than the normal controls. The authors concluded that the patients with atopic dermatitis were more depressive and psychosomatic symptom-prone than the normal control individuals.
Depression in Patients with Asthma
In a study performed by Centanni et al (2000), the anxiety and depression level was tested with State-Trait Anxiety Inventory and ZUNG questionnaires in a population of 80 asthmatic patients. Forty patients with chronic viral hepatitis B or C, and 40 healthy subjects were recruited as control groups, and, subsequently classified in relation to sex, age, and education to parallel the asthmatic sample. The results showed that asthmatic patients had statistically significantly higher scores both in State-Trait Anxiety Inventory and ZUNG when compared with controls. In the ZUNG questionnaire, 27 asthmatic patients (33.8%), 10 patients with liver disease (25%), and 5 healthy controls (12.5%) had higher scores than the cut-off point (40 out of 80), indicating higher traits of depression. As regards both questionnaires, in the asthmatic and healthy populations females had higher scores when compared with men, while among patients with liver disease, the two subgroups showed no gender difference.
Further, in a study performed by Goethe et al (2001) the occurrence of depressive symptoms was evaluated also in a sample of inner-city asthma patients. By using the Center for Epidemiologic Studies Depression Scale, 55% out of 307 asthma patients had scores in excess of the cut-off point for depression (Goethe et al. 2001).
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