Yes, going to church can influence your health according to scientific studies. However, this doesn't say that the same effect can't be achieved by other means, or that the religious part of church going is the determining factor, and not the social or psychological. In other words, all the scientific articles on the subject are merely describing phenomenons and don't analyze them, but saying that more research is needed, which means that the real reasons and factors that affect the health of church goers are yet unknown.
The author of the article seems to suggest this as well, but less willingly:
Social support is no doubt part of the story. At the evangelical churches I’ve studied as an anthropologist, people really did seem to look out for one another. They showed up with dinner when friends were sick and sat to talk with them when they were unhappy. The help was sometimes surprisingly concrete. Perhaps a third of the church members belonged to small groups that met weekly to talk about the Bible and their lives ... A study conducted in North Carolina found that frequent churchgoers had larger social networks, with more contact with, more affection for, and more kinds of social support from those people than their unchurched counterparts. And we know that social support is directly tied to better health.
Healthy behavior is no doubt another part. Certainly many churchgoers struggle with behaviors they would like to change, but on average, regular church attendees drink less, smoke less, use fewer recreational drugs and are less sexually promiscuous than others.
And at the end of the article she calls it placebo and suggests that studying this phenomena would help up use this effect to better people's life.
Eventually, this may teach us how to harness the “placebo” effect ... We do not understand the placebo effect, but we know it is real. That is, we have increasingly better evidence that what anthropologists would call “symbolic healing” has real physical effects on the body. At the heart of some of these mysterious effects may be the capacity to trust that what can only be imagined may be real, and be good.
Sadly, the author doesn't provide the references to all the studies she cites in the article, which makes our job harder, and her arguments less persuasive. And she is a professor in Stanford, she really should know better that this.
The main article on which it's all based is this meta-study by Daniel E. Hall, MD. However the study itself is not too enthusiastic as to the results:
Background: A recent meta-analysis demonstrates a robust but small association between weekly religious attendance and longer life. However, the practical significance of this finding remains controversial.
Conclusion: The real-world, practical significance of regular religious attendance is comparable to commonly recommended therapies, and rough estimates even suggest that religious attendance may be more cost-effective than statins. Religious attendance is not a mode of medical therapy, but these findings warrant more and better quality research designed to examine the associations between religion and health, and the potential relevance such associations might have for medical practice.
The author doesn't suggest that churchgoing is the cure, but that there is something in it that should be studied further.
In the July issue of the same magazine a letter was published by Peter S. Millard, MD, PhD, which says that the study wasn't really good because it disregarded all the other factors that sarround the issue, I really liked it, so I'm citing it fully here:
Dr. Hall bases his analysis on observational data that are of questionable validity. The fact that churchgoers live longer than people who do not attend church may very well have nothing to do with churchgoing but may result from uncontrolled confounding.
Observational studies that showed a benefit of exogenous estrogens in postmenopausal women were debunked by the Women’s Health Initiative Randomized Controlled Trial.1 The accepted explanation for the discrepancy between the observational findings and the experimental results is that women who took estrogens were systematically different from non-users in ways which resulted in improved outcomes (eg, reduced coronary disease).
Barrett-Connor referred to this as the “healthy user effect.”2 The inability to control for the healthy user effect resulted in the biased findings of many observational studies of estrogen use.
Similarly, churchgoers are systematically different from non-churchgoers in ways that are difficult to measure but are likely to result in improved health outcomes that may have nothing to do with churchgoing. Churchgoers are more likely to be employed, have intact families, and are less likely to be homebound by illness or disability. Until the healthy attender effect can be controlled for, it is unwise to attempt to make any inferences about the effect that churchgoing has on health.
The study that claims that churchgoers have a greater social network is probably this one:
Frequent churchgoers report larger social networks, more contact with network members, more types of social support received, and more favorable perception of the quality of their social relationships than do their unchurched counterparts. Farther, most of these empirical patterns withstand statistical controls for a wide range of covariates.
This study suggest that church going can relieve stress, but the more interesting part is that it depends on the church and denomination you go to:
In this study we examined the stress-buffering effect of an intrinsic religious orientation for a community sample of adult Protestant churchgoers. At time 1, participants completed measures of intrinsic religiousness, religious activity, and dysphoria. At time 2, 8 months later, they completed measures of negative life events and dysphoria. For participants from liberal Protestant churches (e.g., Methodist), intrinsic religiousness served as a stress-buffer in the prediction of time 1–time 2 residual change in dysphoria. This effect was nonsignificant for participants from more conservative Protestant churches (e.g., Baptist). Similarly, single-item measures of religion's importance, frequency of prayer, and frequency of church attendance served as stress-buffers for liberal participants, but not for conservative participants. The nonsignificant effects for the latter participants are attributable to their restricted range on the religion variables. The results for the former participants suggest that religious “commitment” is an individual difference variable that influences adjustment to negative life events
Regarding the immune system, there is this study that suggest that male gay HIV-positive churchgoers have a higher T-cell count, which shows that church going affects positively on the immune system
This study examines the relationship between religiosity and the affective and immune status of 106 HIV-seropositive mildly symptomatic gay men (CDC stage B). All men completed an intake interview, a set of psychosocial questionnaires, and provided a venous blood sample. Factor analysis of 12 religiously oriented response items revealed two distinct aspects to religiosity: religious coping and religious behavior. Religious coping (e.g., placing trust in God, seeking comfort in religion) was significantly associated with lower scores on the Beck Depression Inventory, but not with specific immune markers. On the other hand, religious behavior (e.g., service attendance, prayer, spiritual discussion, reading religious literature) was significantly associated with higher T-helper-inducer cell (CD4+) counts and higher CD4+ percentages, but not with depression. Regression analyses indicated that religiosity’s associations with affective and immune status was not mediated by the subjects’ sense of self-efficacy or ability to actively cope with their health situation. The associations between religiosity and affective and immune status also appear to be independent of symptom status. Self-efficacy, however, did appear to contribute uniquely and significantly to lower depression scores. Our results show that an examination considering both subject religiosity as well as sense of self-efficacy may predict depressive symptoms in HIV-infected gay men better than an examination that considers either variable in isolation.
This study however has a very small sample size (try to find a lot of HIV positive gay men that go to church), and should be taken with caution.
This study shows that churchgoing doesn't affect blood pressure, and hypertension, but that prayer increases hypertension, and spirituality increases diastolic blood pressure. This study may contradict the article in some aspects, but it shows that religiosity can affect a persons physical status and health, which (in my opinion) is the main point of the article.
Researchers have established the role of heredity and lifestyle in the occurrence of hypertension, but the potential role of psychosocial factors, especially religiosity, is less understood. This paper analyzes the relationship between multiple dimensions of religiosity and systolic blood pressure, diastolic blood pressure, and hypertension using data taken from the Chicago Community Adult Health Study, a probability sample of adults (N = 3105) aged 18 and over living in the city of Chicago, USA. Of the primary religiosity variables examined here, attendance and public participation were not significantly related to the outcomes. Prayer was associated with an increased likelihood of hypertension, and spirituality was associated with increased diastolic blood pressure. The addition of several other religiosity variables to the models did not appear to affect these findings. However, variables for meaning and forgiveness were associated with lower diastolic blood pressure and a decreased likelihood of hypertension outcomes. These findings emphasize the importance of analyzing religiosity as a multidimensional phenomenon. This study should be regarded as a first step toward systematically analyzing a complex relationship.
And there are some some studies, all show that there can be and is correlation between churchgoing and religiosity and a person's health:
Is going to church good or bad for you? Denomination, attendance and mental health of children in West Scotland
Is Church Attendance Associated With Latinas' Health Practices and Self-reported Health?
Like every aspect of human life, churchgoing and religion may have affect on our health, but the mechanism behind it, the reasons and what aspects of our health are affected are still unknown, and require much more high quality research. All the study that available today, don't try to explain the phenomenon only to describe it.
A serious study, which will be able to make the right differentiation of the elements that are unique to religion and churchgoing, is still needed, and until it's done, we can't say what is the aspect of this particular activity that has affect on us.