Objectives Depression has been linked to risky sexual behaviours in adolescents, but there is little research among adults. The goal of this analysis was to examine the associations between current depression and self-reported risky sexual behaviours in a nationally representative sample of US adults aged 20–59 years. The authors also examined the association between depression and infection with herpes simplex virus type 2 (HSV-2), a biological marker of risky sexual behaviours.
Methods The authors used data from the 2005–2008 National Health and Nutrition Examination Surveys. Current depression was measured by the Patient Health Questionnaire-9. Antibodies to HSV-2 were tested using the enzymatic immunodot assay. The authors used logistic regression to examine the associations controlling for socio-demographic variables.
Results Among 5273 adults aged 20–59 years, 7% had depression, 36% reported 10 or more lifetime sex partners, 15% had two or more past-year sex partners and 13% had first sex before 15 years of age. Persons with each of the risky sexual behaviours were more likely to have depression than those without. In stratified analyses, risky sexual behaviours were associated with depression in women but not in men. Among 3940 adults aged 20–49 years, 19% had HSV-2 infection. Persons with HSV-2 infection were more likely to have depression (OR 2.1, 95% CI 1.5 to 2.9).
Conclusions Risky sexual behaviour is related to current depression in adult women. Healthcare providers should be aware of this association and its potential implications in order to deliver better care for patients with depression or sexually transmitted infections.
- herpes simplex virus type 2
- sexual behaviour
- epidemiology (general)
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Many studies have examined the relationship between depression and risky sexual behaviour in adolescence and young adulthood.1–8 Although there are some exceptions, the majority find that the two are related in the 12–24 age group. Studies examining the relationship between depression and risky sexual behaviour in adults older than 25 years of age are uncommon, with the exception of studies focusing on high-risk groups, such as men who have sex with men or intravenous drug users.9 10
Sexually transmitted infections (STIs) are often outcomes of risky sexual behaviours. Studies of adolescents and at least one study of adults have found that depression is related to STIs.4 5 8 11 12 Most studies, however, have not validated self-reported history of STIs with laboratory testing.4 5 12
The goal of this study is to examine the association between risky sexual behaviour and current depression in a nationally representative sample of US adults aged 20–59 years. Because sexual behaviours were self-reported and may be subject to reporting and recall biases, while herpes simplex virus type 2 (HSV-2) is an objective biological marker of STI risk, we also examine the association between depression and HSV-2 infection to further confirm the association between risky sexual behaviour and depression. The relationship between depression and HSV-2 infection was examined in adults aged 20–49 years.
This study uses data from the 2005–2008 National Health and Nutrition Examination Surveys (NHANES).13 NHANES is a nationally representative survey conducted continuously by the US National Center for Health Statistics (NCHS). NHANES is approved by the NCHS Research Ethics Review Board. This study is a secondary analysis of publicly available NHANES data.13 NHANES is a complex, stratified, multistage probability sample survey designed to measure the health and nutritional status of the US civilian non-institutionalised population. In 2005–2006, non-Hispanic black persons, Mexican–American persons, adults aged 60 years and over and low-income persons were over-sampled to improve the statistical reliability of the estimates for these groups. In 2007–2008, the same groups were over-sampled except that all Hispanic persons were over-sampled rather than only Mexican–Americans.
The average unweighted response rate for examination at the Mobile Examination Center (MEC) for persons 20–59 years old was 74% with a sample size of 6947. We excluded 191 persons who reported never having had sex from this analysis. We also excluded persons who did not have information on at least one of the three risky sexual behaviours, depression or poverty.
There were 1170 people with missing values on sexual behaviour. Non-Hispanic Caucasians and women were less likely to have missing values than persons of other race/ethnicity and men, respectively. There was no difference in the percentage with missing values by age or marital status. Only three additional people were excluded because of missing values on depression. An additional 310 respondents were excluded because of missing values on poverty. Thus, the sample size for analyses examining depression and risky sexual behaviour was 5273.
For the HSV-2 analyses, an additional 221 persons were excluded due to missing or indeterminate HSV-2 testing results. Also, because persons aged ≥50 years were not tested for HSV-2, 1112 persons were excluded for the HSV-2 analysis. Thus, the sample size for models looking at depression and HSV-2 infection was 3940.
Participants were interviewed first in their home and then underwent additional interviewing and a health examination at the MEC. Participants who came to the MEC were compensated for their time and also received a report on the results of their medical examination. Depression questions were administered by an interviewer in a private face-to-face interview at the MEC. Questions on sexual behaviour were answered in a private room at the MEC using the Audio Computer-Assisted Self-Interview system.
Depression was measured using the Patient Health Questionnaire-9 (PHQ-9), a nine-item screener that asks questions about the frequency of symptoms of depression over the past 2 weeks.14 In the PHQ-9, response categories ‘not at all’, ‘several days’, ‘more than half the days’ and ‘nearly every day’ are given a score ranging from 0 (not at all) to 3 (nearly every day). A total score is calculated ranging from 0 to 27. Depression was defined as a PHQ-9 score of 10 or higher, a cut point that has been well validated and is commonly used in clinical studies that measure depression.14
This study is limited to adults aged 20–59 years. The risky sexual behaviours assessed were age at first sex, number of lifetime sex partners and number of sex partners in the past year. Blood samples were obtained as part of the health examination, and antibodies to HSV-2 in persons aged 20–49 years were tested using enzymatic immunodot assay with purified glycoprotein gG-2, which is specific for HSV-2 as the antigen.15
Chi-square tests were performed to examine the relationship of current depression with each risky sexual behaviour and with the socio-demographic variables. T tests were performed for variables with multiple levels using a p value of <0.01 to indicate statistical significance because of the multiple comparisons. Logistic regression models were used to examine the relationship of each risky sexual behaviour with depression while controlling for demographics. Although the cross-sectional nature of the data makes it impossible to evaluate temporal relationships, depression was chosen as the dependent variable in the logistic regression models because it is the most current of our variables of interest, measuring depression in the 2 weeks prior to the interview.
The literature has shown that the prevalence of both depression and risky sexual behaviours varies by sex and race/ethnicity. We assessed the presence of effect modification using interaction terms in our logistic models and detected potential effect modifications by sex on age at first sex (p=0.05) and by race/ethnicity on the number of sex partners in the past year (p=0.06) (data not shown). Based on these findings, we conducted logistic regression models stratified by sex and race/ethnicity.
Finally, we include the three risky sexual behaviour measures in the same model to determine which ones remained significant when controlling for the others.
We also examined the relationship between HSV-2 antibody status and depression, alone, then adjusting for socio-demographic variables and finally adjusting for socio-demographics and all the risky sexual behaviours.
To make the estimates nationally representative of the non-institutionalised population in the USA, we used NHANES participants' sample examination weights, provided by NCHS, which account for the differential probabilities of selection, non-response and non-coverage, for all analyses. All analyses were conducted using the SUDAAN software package that incorporates the survey's complex sample design and the weights.16
Prevalence of current depression
The overall prevalence of current depression in 20–59-year-olds was 7.2% (table 1). Depression was more common in women than in men and in persons aged 50–59 years as compared with persons aged 20–29 years (table 1). Depression was associated with being unmarried, living in poverty and having high school or less education. Depression was associated with all three risky sexual behaviours that we examined. Among persons who had their first sexual experience before the age of 15, 14.8% had current depression as compared with 6.1% of persons who were older at their initial sexual experience. Persons with one to three lifetime sex partners were less likely to be depressed than those with more lifetime partners. Persons with one sex partner in the past year were less likely to be depressed than those with zero or two or more sex partners in the past year (table 1).
Prevalence of risky sexual behaviours
Having 10 or more lifetime sex partners, reported by 35.9% of the population, was the most prevalent risky sexual behaviour. First sex at younger than 15 years of age and two or more sex partners in the past year were reported by 13.4% and 15.2% of the population, respectively. Only 3.3% of respondents reported all three risky sexual behaviours, and 13.1% reported two of the three behaviours. Slightly more than half the population (54.9%) had no risky sexual behaviours (data not shown).
Persons with depression were more likely to report risky sexual behaviour than those without depression: 27% of those with depression had first sex at younger than 15 years of age as compared with 12% of those without depression. Men were more likely to have had multiple sex partners than women were. Non-Hispanic African–Americans were more likely to have had first sex at younger than 15 years of age and two or more partners in the past year than persons of other race/ethnic groups (data not shown).
In a supplementary analysis, we examined the relationship of a four-category depression severity variable (PHQ-9 scores 0–4, 5–9, 10–14 and 15+) to each of the risky sexual behaviours. There was some evidence of a dose–response relationship from no depressive symptoms (PHQ-9 scores 0–4) to mild symptoms (scores 5–9) to depression. After the cut-off for depression (10+), there was no evidence of a further trend by depression severity. Tests for linear trend were significant for the depression severity variable with each risky sexual behaviour (see online table).
Logistic regression models were used to examine the relationship of each risky sexual behaviour with depression separately, after adjusting for age (four categories), sex, race/ethnicity (four categories), being married or not, living in poverty and having a high school education or less. Overall, each behaviour was associated with about a two times greater odds of depression (table 2). In models stratified by sex, the association between risky sexual behaviours and depression was statistically significant for all three measures in women but was not significant in men. We further examined these associations in models stratified by race/ethnicity. In non-Hispanic Caucasians, all three risky behaviours were associated with depression. In non-Hispanic African–Americans, having 10 or more lifetime sex partners compared with one to three partners was associated with a two times higher odds of depression, while first sex prior to age 15 was associated with a two and a half times higher odds of depression. Only early age at first sex was associated with depression among Mexican–Americans. In women and in all three race/ethnicities, having sex at younger than 15 years of age was associated with depression. In each race/ethnicity group, when further stratified by sex, the above relationships were significant only in women (data not shown).
In a model containing all three risky behaviours, persons who had sex for the first time before the age of 15 had 2.1 times the odds of having depression compared with those who had a later sexual debut (table 3). Associations of lifetime partners and past-year partners with depression were attenuated after adjustment for the other two risky sexual behaviours. When stratified by sex, in women, but not in men, number of lifetime partners and age at first sex were associated with depression.
The prevalence of HSV-2 was 19.2% and increased with the number of lifetime sex partners. The prevalence of HSV-2 was higher in persons with zero or two or more sex partners in the past year and in those who had first sex at younger than 15 years of age. The crude OR for depression associated with HSV-2 was 2.1 (95% CI 1.5 to 2.9). After adjusting for socio-demographic variables, the relationship was attenuated with an OR of 1.4 (95% CI 0.9 to 2.1). Finally, after adding the three risky sexual behaviours to the model, the OR for depression associated with HSV-2 no longer approached significance. Of the three risky sexual behaviours, only early age at first sex remained significantly associated with depression after HSV-2 was added to the model (data not shown).
This study demonstrates that in women aged 20–59 years, sexual behaviours that took place in adolescence (early age at sexual initiation) as well as lifetime sexual behaviours (lifetime partners) and more recent risky sexual behaviour (past-year partners) are related to current depression. It also shows a relationship between a laboratory-confirmed STI (HSV-2) and depression. Studies have shown that there is a relationship between risky sexual behaviours and depression in adolescence and young adulthood.1–8 The present study shows that the relationship also exists in adult women.
This study has a cross-sectional design, making it impossible to evaluate the temporal relationships. Other studies have tried to do so, however. In some of the prospective studies of adolescents and young adults, depression led to risky sexual behaviour,3 4 while other prospective studies of adolescents and young adults found risky sexual behaviour led to depression.5 17
Longitudinal studies of the course of depression demonstrate that the illness has an episodic course characterised by chronicity and relapse. Approximately 25% of cases of major depression have an age of onset of 19 or younger, including 10% by age 14.18 Studies have also shown that having one's first episode of depression in childhood or adolescence is associated with a more chronic course. One 12-year prospective study showed that subjects spent 59% of follow-up with depressive symptoms19; thus, adults with current depression may very likely have had depression when they were younger. The early onset of depression may have led to early first sexual experience as well as a larger number of lifetime sex partners, the findings we observed in this study. The opposite cause and effect is also possible as the consequences of risky sexual behaviour, such as unplanned pregnancy and STIs, may trigger depression in susceptible individuals. It is also possible that the relationship is bi-directional as has recently been demonstrated with diabetes and depression.20 21
Another possibility is that a third factor may be related to both depression and risky sex. Early age at first sex was strongly associated with current depression. Factors that predispose to early first sex, such as family disorganisation, poverty and substance abuse,22 may also predispose to depression. In another example, having two or more past-year partners might be related to a divorce or separation which could also trigger an episode of depression in susceptible individuals.
Among women aged 20–59 years, each risky behaviour is related to current depression. The relationships are not significant in men, however. This could be because there is more stigma attached to risky sexual behaviours in women.12 It could also be because women are more likely to suffer the consequences of risky sexual behaviours, such as STIs and unintended pregnancies. Self-destructive behaviour is a frequent manifestation of depression, and risky sexual behaviour may be seen as self-destructive more by women than by men. Other studies that have examined gender differences have also found the relationship between depression and risky sexual behaviours to be more consistent in women or girls1 2 8 with rare exceptions.5 The relationship between depression and STIs was more consistent in women in one study,12 but another study found the relationship between depression and STI to be significant only in black men.8
In the models stratified by race/ethnicity, lifetime partners and age at first sex were associated with depression among both non-Hispanic African–Americans and non-Hispanic Caucasians. Only age at first sex was related to depression in Mexican–Americans, however.
Because HSV-2 infection is almost exclusively sexually transmitted and cannot be cured, so healthcare-seeking behaviour does not affect its prevalence, seroprevalence of HSV-2 infection is a cumulative biological marker for sexual risk. In our study, the relationship of HSV-2 and depression further validates the relationship between depression and self-reported risky sexual behaviours. It should be noted that this association was attenuated after adjustment for socio-demographic variables and no longer approached significance when sexual behaviours were added to the logistic regression models, suggesting that HSV-2 is related to depression through risky sexual behaviours. Although genital herpes is associated with significant stigma, many persons infected with HSV-2 do not have symptoms and most (>80%) are unaware of their infection,23 and thus, it is unlikely that the infection itself contributes directly to the development of depression.
One nationally representative study from Canada demonstrated a relationship between depression and STIs in adulthood, but STIs were measured by self-report.12 Two studies of small patient groups that looked specifically at the relationship between depression and laboratory-confirmed HSV had conflicting results. A group of patients with depression were not more likely to have HSV (either type 1 or type 2) than healthy controls.24 In a study of patients with coronary heart disease, on the other hand, depression was found to be related to pathogen burden, including herpes simplex viruses.25
This study has several limitations. Twenty-four per cent of respondents had missing data, mainly on sexual behaviours. Because two of the groups with missing data, men and non-Hispanic African–Americans were more likely to have HSV-2 and to report risky sexual behaviour, the missing data are not random and may bias the results. It is unclear, however, what effect the missing data would have on the relationship between risky sexual behaviour and depression. Because HSV-2 data were only available for ages 20–49, models including HSV-2 had a smaller sample size than the other models, resulting in decreased power for the HSV-2 analyses. Persons in treatment for depression may have been misclassified in our analyses as not having depression. Information on treatment as well as on self-reported history of depression, beyond the 2 weeks covered by the PHQ-9, would have been useful. As discussed above, the data are cross-sectional, making it impossible to draw conclusions about temporal relationships. Another limitation was the lack of information about safer sex practices, such as condom use.
A longitudinal study in adults with more frequent ascertainment of depression and sexual behaviour as well as laboratory-confirmed STI may help clarify questions raised in our study. Qualitative research such as in-depth interviews with respondents who reported both depression and risky sexual behaviour may also provide further insights into the relationship.
Risky sexual behaviours are related to depression in adult women. This finding may have implications for those providing treatment for depression or STIs. Healthcare providers should be aware of this association and its potential implications in order to deliver comprehensive and better care to patients with depression or with STIs. The integration of mental health and sexual health services at the clinic level has also been recommended.4 8 10 12
Adult women with a history of risky sexual behaviour were more likely to have current depression than were women without such a history.
Persons with herpes simplex virus type 2, a biological marker for sexual risk, were more likely to have current depression.
Monitoring for depression among persons with risky sexual behaviour, such as persons attending sexually transmitted infection clinics, may identify persons who would benefit from depression treatment.
Assessing sexual behaviour of persons in treatment for depression may identify persons who would benefit from safer sex counselling.
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Disclaimer The findings and conclusions in this paper are those of the authors and do not necessarily represent the views of the National Center for Health Statistics or the National Center for HIV/AIDS, Viral Hepatitis, STD and TB Prevention, Centers for Disease Control and Prevention.
Competing interests None.
Patient consent Respondents to the survey gave signed consent at the time of data collection. Currently all data used in this study are completely de-identified and are publicly available on the NCHS web site.
Ethics approval NCHS Research Ethics Review Board approved original data collection. All data are now publicly available for research.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement All data used in this study are publicly available on the NCHS web site.