A of the Relating to Gender Differences in Major Depressive Disorder - Literature review Example

A Critical Evaluation of the Empirical Evidence For The Proposal That the Prevalence and Expression Of, and Risk Factors For, Major Depressive Disorder Are Different For Women, Compared To Men Abstract This paper presents a critical review of the literature relating to gender differences in major depressive disorder. The author begins by identifying the state of research into the prevalence and expression of, and risk factors for, major depressive disorder are different for women, compared to men in 1988. It then provides a brief definition of major depressive disorder. Subsequently, the research (with the focus on the last decade) into gender differences in depression is outlined and discussed. A significant section is devoted to research involving opposite sex dizygotic twin pairs an another considers the gender differences in late-life depression. The paper concludes with consideration of the implications of the current state of knowledge for future research and future clinical practice. Introduction Frank, Carpenter and Kupfer published an article in the American Journal of Psychiatry in 1988, entitled, “Sex Differences in Recurrent Depression: Are There Any That Are Significant?” The title of this article is telling. The authors' phrased the title as a question. They were investigating whether or not sex differences in recurrent depression were significant. They were not discussing the differences in risk factors or the differences in duration of depressive episodes, they were considering whether any differences were significant. This implies that gender differences in depression were a subject suitable for investigation, that gender differences in depression did in fact exist in a significant manner. (Frank, Carpenter and Kupfer, 1988) Their research involved a sample of 180 men and women recruited through a variety of sources including self-referral, medical referral and in response to a public information campaign. They subjected their subjects to a battery of tests at an initial screening. They were tested again at the completion of a period of 16 weeks of acute treatment. They concluded that some tests indicated a significantly higher score for women on some tests, such as self-reporting, yet no significant differences on other tests such as the traditional 17-item Hamilton scale. The majority of the study group were women. Overall, they concluded that men and women demonstrated gender differences in depression at various stages throughout the treatment process but at the end of the treatment process they reported “significant sex differences on the depression factor had disappeared”, “there was no difference between sexes in the likelihood of achieving recovery by the end of 16 weeks” and “there was no significant difference in the number of treatment terminators in each group [men and women].”This observation is quoted verbatim because of its significance. Amongst their sample, at the conclusion of a 16 week acute treatment intervention they found no significant gender differences in depression amongst men and women. This conclusion, acceptable in 1988, has in the last twenty-five years become rather less than the accepted norm. Currently, gender differences in depression, significant differences in depression, in everything from risk factors to duration of episodes and symptomology have become accepted. According to a review article by Piccinelli and Wilkinson (2000) epidemiological differences in the prevalence of depression, in its morbidity across all of its diagnostic subtypes and in age of onset (earlier for women) are established. The following discussion will present a critical review of the literature relating to this increased prevalence of depression in women. This critical review will consider a variety of aspects of, and factors in, depression in the context of gender comparisons. Subsequently, the implications of the current state of research into gender differences in depression, in terms of both research and clinical applications will be considered. Definition of Major Depressive Disorder According to the DSM-V major depressive disorder is present when at least 5 of the following symptoms are present, during a given two week period: Depressed mood, nearly every day during most of the day. Marked diminished interest or pleasure in almost all activities. Significant weight loss (when not dieting), weight gain, or a change in appetite. Insomnia or hypersomnia (excess sleep). Psychomotor agitation or psychomotor retardation. Fatigue or loss of energy. Feelings of worthlessness or inappropriate guilt. Impaired ability to concentrate or indecisiveness Recurrent thoughts of death, recurrent suicidal Additionally, these symptoms must represent a change from previous levels of functioning. In other words, major depressive disorder is present when five of the preceding nine symptoms are present and present in a manner that represents a significant departure from the individuals previous circumstances psychological profile. Prevalence of Major Depressive Disorder Analyzing World Mental Health Surveys, Seedat et al. (2009) conclude that major depressive disorders are significantly higher amongst women than men. However, they also note that the differences in occurrence of major depressive disorder are narrowing significantly. They also tentatively correlate this narrowing of the prevalence of major depressive disorder to variations in the traditionality of female gender roles. Nonetheless, a significant difference persists even if it is narrowing. Once considered a subject for debate it, it is now established that major depressive disorder is more prevalent among women than men. (Piccinelli and Wilkinson, 2000). Mule concurs with this assertion that women have higher rates of depression than do men. (n.d.) Mule also asserts that the question is no longer do women exhibit a greater prevalence of major depressive disorder than men, but rather, why, how is it manifest, how is it best treated and other related questions. The remainder of this discussion will be based on the acceptance of a difference in the frequency of major depressive issues between men and women and turn its attention to a review of the literature and research related to the questions of why and how. Gender Differences in Depression An important starting point is Silverstein's (1999) research into differences in depression associated with somatic symptom differences between genders. Silverstein investigated, through a critical review of existing data, differences between somatic depression and pure depression. Silverstein defines somatic depression as depression manifest in fatigue, eating disturbance and sleep disruption. He defines pure depression as depression manifest in other symptoms but not predominantly in somatic symptoms. Silverstein drew data from the Epidemiologic Catchment Area (ECA) study and the National Comorbidity Survey conducted in the United States. His criteria for defining a major depressive episode was persistence over a minimum of six months. Somatic depression was defined as that demonstrating all three characteristics of somatic depression (fatigue, eating disturbance and sleep disruption) and non-somatic or pure depression as any depression exhibiting less than all three of the somatic symptoms. His results indicated that the occurrence of somatic depression was more than twice as prevalent among men than women (7.6% as opposed to 3.6%). Further, he determined that the occurrence of pure depression was not significantly different between men and women. Therefore, he determined that the difference in rates of major depressive disorder between men and women was accounted for by the greater frequency of a sub-group of depression, namely somatic depression amongst women. However, he also acknowledged that more detailed research would be required to clarify the nature of the differences in terms of specific symptoms. A great deal of research considers the links between gender expectations and social roles. Weich, Sloggett and Lewis (1998) examined this link using the 1991 British Household Panel Survey (BHPS). The BHPS assessed mental disorders using the 12-item General Health Questionnaire and social roles through self-reporting. Their study group was a cross sectional survey of 5.574 adults (16-74 years). Their research indicated that major depressive disorder was more common among women than men and most common amongst women in high load roles – caring for people with a disability and with primary responsibility for child care an/or household chores). However, in an interesting 'Catch-22' they acknowledged that this finding was based on self-reporting of social roles and that women may not actually fill high load roles but rather perceive of themselves filling these roles or feel a gender role related responsibility to report that they fulfill these roles. This possibility means that their findings might be inaccurate. They conclude that further research based on measures other than self-reporting to identify social roles is necessary to confirm or refute their findings. Despite the tentative nature of Weich, Sloggett and Lewis's (1998) conclusions other researchers have reached similar conclusions. Mule (n.d.)assesses the research into a wide variety of theories of depression and describes the sex-/gender-role identity difference theory as the “best answer” to the prevalence of depression amongst women as opposed to men. Surveying existing research she concludes categorically that environmental factors, “gender stereotypes and identity roles” make women more susceptible to major depressive disorders. The counter-argument, however, is presented succinctly in a peer commentary by Josiah P. Allen, “It's not easy being male either”. Unfortunately, Mule's paper seems to be simply ideologically driven and one is left with the sense that her conclusion is a statement of faith rather than the product of scientific inquiry and empirical analysis. A counterpoint to the gender role theory is provided by Parker and Brotchie's research into the biological basis of gender differences in depression. They present a physiological explanation for women's increased susceptibility to anxiety disorders, and describe the increased prevalence of women to depression as an outcome of this biological predisposition to anxiety. They argue that women experience different post-pubertal gonadal hormone development (particularly as it relates to estrogen levels) than men, and that this predisposes them to limbic system hyperactivity with the consequence of increased levels of anxiety and, consequently, depression. On a theoretical and physiological level this theory offers some potential. This may be a promising avenue of research but it can only be described as tentative on the basis of this paper and requires extensive experimental examination. A great deal of research has been conducted into gender differences in the emergence of depression in preadolescents and adolescents. Hankin et al. (1998) conducted a 10-year longitudinal study into the development of depression from preadolescence to young adulthood (ages 11 to 21). There study sample came from the Dunedin (New Zealand) Multidisciplinary Health and Development Study. Potential methodological problems focused on the differing measures that are used for 11 and 21-year-olds. They report that gender differences emerge at ages 13 to 15, but increase significantly in the 15 to 18 age group. The rate increases for both genders but doubles for females, far outpacing the increase in males. They suggest that the risk for women is highest than at any other age. There results also showed that there is no significant difference between populations that finish their education during this period and those that continue their education regardless of gender. Hankin (2009) examined sixth to tenth graders. Results showed that females show higher rates of depression at sixth grade and increasing trajectories of depression for females throughout the study period. Together these studies indicate that even at a very young age females demonstrate a greater incidence of depression that males and that the gender gap increases as children move through adolescence and into young adulthood. In both incidences Hankin notes that the majority of the information comes from self-reporting measures and that these studies need to be replicated with multiple methods and informants. Mezulis et al. (2009) applied the cognitive vulnerability-stress model to gender differences in adolescent depression rates. Their research was a part of the ongoing Wisconsin Study of Families. The Children's Depression Inventory (CDI) prepared for use in children aged 8 to 17 was the assessment tool. Results indicated significant levels of depression at all ages, with females demonstrating higher levels. However, significantly greater stressors were only evident for women in the 15 to 17 age cohort. They also observed that the difference in gendered levels of depression is not directly related to increased stressors as the increased stressors only emerge after increased female rates of depression are evident. They conclude that their research does not support the vulnerability or exposure models of adolescent depression rates. Similar research, using a Canadian study group, by Galambos, Leadbeater and Barker (2004) confirmed that adolescent females exhibit higher rates of depression (double the rate for males a other studies have found) although they did not find that rates of depressive episodes increase from age 12 to 19. Their research identified various risk factors but did not identify any risk factors statistically more prevalent for males than females. Research by Conley and Rudolph (2009) analyzed puberty in terms of timing and peer support in the onset of adolescent depression. The sample group consisted of 158 youth aged nine to fifteen. Interestingly, early onset puberty was linked to female adolescent depression while late onset puberty was linked to male adolescent depression. The study also linked late onset puberty for males as a source of peer stress and early onset puberty as a source of peer stress for females. Therefore, the study concludes the differing ages of puberty onset may make a social contribution to depression (as a result of peer relations) rather than have a biological basis. Incidentally, research has also identified gender differences in suicidal acts related to major depression. Oquendo et al. note that men are less likely to attempt suicide than women but more likely to be successful than women. (2007) Their research also demonstrates than women who have attempted suicide are statistically significantly more likely to attempt suicide again while men are not. They are more likely to attempt suicide again than those who have never attempted suicide but not in a statistically significant manner. Both men and women who are depressed are more likely to commit suicide than people who are not depressed. Both men and women who have attempted suicide once are more likely to attempt it again than those who have never attempted suicide. However, women who have previously attempted suicide are statistically more likely to succeed at a second attempt than men. A Special Case: Opposite-Sex Dizygotic Twin Research Research into opposite-sex dizygotic twins has tremendous potential because of the epidemiological similarities of the sample group. Potential external variables such as age, family of origin, socio-economic background and parental circumstances are eliminated as the twin-pair share these characteristics. (Khan, Gardner, Prescott and Kendler, 2002) That said, there is one significant problem in conducting these studies. Finding a sample group of opposite-sex dizygotic twins reduces the potential population sample considerably. That is a complicating factor but not an insurmountable difficulty. When Khan, Gardner, Prescott and Kendler conducted there study in 2002 they described it as the first study into gender differences in major depression conducted on a matched, epidemiological sample. The authors examined only symptoms of depression and used a sample of white twins drawn from the Virginia Twin Registry. They used structured interviews to assess the 14 disaggregated symptoms of depression during the subjects 'worst' episodes of major depression. They used McNemar's chi-square analysis and conditional logistic regression to analyze their data. This analysis revealed significant differences in the symptoms of depression between men and women. Female twins reported significantly more fatigue, hypersomnia and psychomotor retardation. For men symptoms of insomnia and agitation are more prevalent. Overall, these findings indicate a different response to depression amongst men and women. This research was expanded upon by Middledorp et al. (2006) In a study reported in Twin Research and Genetics they examined symptoms in opposite-sex dizygotic twins and compared the results to both sibling pairs and unrelated individuals. They described differing constellations of symptoms as 'different pathways' to, and through, depression. Their sample of approximately 3,500 subjects was drawn from the Australian and Netherlands Twin Registers. Therefore it also offers a comparison of different cultural groups in terms of depression relative to the previously referenced research. Particularly since both studies used similar methods, structured telephone interviews. They used univariate logistic reference to statistically analyze their data with symptoms as the dependent variable and gender as the independent variable. Overall, they noticed a higher incidence of depression amongst their older, Australian sample. More importantly, their findings differed significantly from the earlier research of Khan et al. The only significant difference in symptoms that they noted was amongst unrelated individuals. In that comparison women were more likely to experience weight loss than men. In all other comparisons and with reference to all other symptoms they reported that men and women have similar major depression symptom profiles. This clearly contradicts the findings of the previous research. This is not to say that it discredits the previously reported study: Rather, it indicates that further research needs to be conducted in this potentially rewarding avenue of examination. Further, it is important to note again that the study subjects were from different geographic and cultural groups and this may be an important factor in the different findings. Gender Differences in Depression in Late Life There are clear indications that the manifestation of major depressive disorder varies with age. In general, depression sees to be most common amongst adolescents and people in mid life and less common amongst people in early adulthood and late life. For example, Weich, Sloggett and Lewis (1998) found depression to be most common among adults in those aged 16-54 and less common amongst those aged 55-74. Ryan et al. (2008) examined depression in late life. Specifically, the morbidity rate amongst depressed individuals in late life was examined with the independent variables being antidepressant use and gender. The sample consisted of 7,363 community dwelling individuals in late life in the three cities in France. Depression was measured using the Mini-International Neuropsychiatry Interview and the 20-item Centre for Epidemiology Studies Depression Scale. The follow-up time for the mortality analysis had a median of 3.7 years. Statistical analysis of their data revealed that both antidepressant use and gender had a 'striking' impact on the results and that the differences were significantly different even after controlling for a large number of variables. They concluded that the highest risk for mortality was among depressed men using antidepressants. Amongst males, severity of depression was also a variable that increased the risk of mortality. Amongst women it was only increased severity of untreated depression that was linked to increased mortality. (Ryan et al., 2008) The authors identify a variety of potential links between depression and mortality including depression's exacerbation of other medical illnesses, inability to follow prescribed medication regimens, loss of motivation and social isolation. Implications This critical review of the literature into gender differences in major depressive disorders offers many results and tentative conclusions. Also, it has many implications for future research and for clinical practice. 1. In virtually everyone of the studies considered the majority of the sample group were female. Implicit in this fact is the risk of inaccuracies in statistical comparison. Frank, Carpenter and Kupfer (1988) studied 180 women and only 50 men. Almost twenty years later Ryan et al. (2006) examined a study group that was slightly more than sixty percent female. Therefore, going forward, research must aim to identify and study sample populations in which the balance between male and female study subjects is more numerically balanced. 2. As noted above research into gender-opposite dizygotic twins has tremendous potential because of the epidemiological similarities of the sample group. On the other hand, this research is very difficult as the potential sample members are limited. Regardless, future research with sex-opposite dizygotic twins is extremely important and further research in this area would prove fruitful. 3. Research into depression, its occurrence and its implications amongst persons in late life seems to be rather limited. This is a situation that requires further examination. This is particularly true as life spans are increasing and the proportion of individuals in later life is occurring across the world. The costs and broader impacts of depression amongst those in late life will increase as their proportion of the population increases. Therefore, research into this aspect of the phenomenon is a matter of public health and public policy concern. In particular research into the links between depression in later life and mortality requires examination with attention to gender differences and antidepressant medication. (Ryan et al., 2008) 4. Silverstein (2008) presents significant gender differences between somatic and non-somatic or pure depression. However, he also notes that further research is necessary to delineate the nature of this difference. Therefore, further research to define this difference is necessary. 5. Many studies have linked the prevalence of major depressive disorder amongst women to roles and social expectations. This research indicates a link between the two. However, there is also clear recognition that this subject requires further examination. 6. Seedat et al. (2009) correlate the narrowing of the prevalence of major depressive disorder to variations in the traditionality of female gender roles. However, they also note that this narrowing is not widely understood and requires additional research. Therefore, additional research into this area is a high priority, particularly since this shift in traditional female roles will continue in the future. 7. Parker and Brotchie's research into the biological basis of gender differences in depression appears promising. However, extensive experimental investigation would be required to confirm their purely theoretical speculation. Reference List Conley, Colleen S. and Rudolph, Karen D. (2009). The emerging sex difference in adolescent depression: Interacting contributions of puberty and peer stress. Developmental Psychopathology, 21 (2), 593-620. Frank, Ellen, Carpenter, Linda L., and Kupfer, David J. (1988). Sex Differences in Recurrent Depression: Are There Any That Are Significant? American Journal of Psychiatry, 145 (1), 41-45. Galambos, Nancy L., Leadbetter, Bonnie J and Barker, Erin T. (2004). Gender differences in and risk factors for depression in adolescence: A 4-year longitudinal study. International Journal of Behavioral Development, 28 (1), 16-25. Hankin, Benjamin L. (2009). Development of sex differences in depressive and co-occurring anxious symptoms during adolescence: Descriptive trajectories and potential explanations in a multi-wave prospective study. Journal of Clinical Child & Adolescent Psychology, 38 (4), 460-472. Hankin, Benjamin L. et al. (1998). Development of Depression From Preadolescence to Young Adulthood: Emerging Gender Differences in a 10-Year Longitudinal Study. Journal of Abnormal Psychology, 107 (1), 128-140. Kahn, Amir A., Gardner, Charles O., Prescott, Carol A. and Kendler, Kenneth S. (2002). Gender Differences in the Symptoms of Major Depression in Opposite-Sex Dizygotic Twin Pairs. American Journal of Psychiatry, 159 (8), 1427-1429. Mezulis, Amy H., Funaski, Kristyn S., Charbonneau, Anna M. and Hyde, Janet Shibley. (2009). Gender Differences in the Cognitive Vulnerability-Stress Model of Depression in the Transition to Adolescence. Cognitive Therapy and Research. Middeldorp, Christel M. et al. (2006). Sex Differencess in Symptoms of Depression in Unrelated Individuals and Opposite-Sex Twin and Sibling Pairs. Twin Research and Human Genetics, 9: (5), 632-636. Mule, Christina M. (n.d.) Why Women are More Susceptible to Depression: An Explanation for Gender Differences. Www.personality.org/papers/mule.html. Retrieved 01-11-2010. Oquendo, Maria A. (2007). Sex Differences in Clinical Predictors of Suicidal Acts After Major Depression: A Prospective Study. American Journal of Psychiatry, 164 (1), 134- 131 Parker, Gordon Barraclough and Brotchie, Heather Lorraine. (n.d.) From Diathesis to Dimorphism: The Biology of Gender Differences in Depression. Piccinelli, Marco and Wilkinson, Greg. (2000). Gender Differences in Depression. The British Journal of Psychiatry, 177, 486-492. Ryan, Joanne et al. (2008). Late-life depression and mortality: influence of gender and antidepressant use. British Journal of Psychiatry, 192, 12-18. Seedar, Soraya et al. (2009). Cross-National Associations Between Gender and Mental Disorders in the World Health Organization World Mental Health Surveys. Archives of General Psychiatry, 66 (7), 785-795. Silverstein, Brett. (1999). Gender Differences in the Prevalence of Clinical Depression: The Role Played by Depression Associated With Somatic Symptoms. American Journal of Psychiatry, 156 (3), 480-482. Weich, Scott, Sloggett, Andrew and Lewis, Glyn. (1998). Social roles and gender difference in the prevalence of common mental disorders. British Journal of Psychiatry, 173, 489-493. Read More