Obesity and overweight are increasingly a topic of concern for patients with severe mental illness (McElroy, 2009
). In this study, we prospectively examined change in BMI using a continuous measure, cBMI, and its effects in female subjects with BPD.
Three main findings have emerged from this study. The first finding concerns core psychological symptoms of BPD. In previous reports, we have shown that overall our subjects have become less symptomatic over time (Zanarini, Frankenburg, Reich, & silk, Hudson, & McSweeney, 2007
), and this is apparent in the prevalence figures we found. But a different picture emerges when we examined the relationship with BMI. We found that there was a significant relationship between changes in cBMI and subjects reporting self-mutilation and high levels of dissociation (but not suicide attempts).
The significant relationship between change in cBMI and adverse psychological outcomes represents a new finding. It may be that those patients with BPD with more severe and more chronic symptoms are more likely to be gaining weight due to being less active and taking multiple psychiatric medications (Frankenburg & Zanarini, 2006
). It may also be that they are more likely to have a family history of obesity in first-degree relatives (Frankenburg & Zanarini, 2006
). Whether this family history of obesity represents a biological vulnerability, social learning, or some combination of the two is an open question. A possible confounding factor is the effect of childhood adversity. It is possible that weight gain for some of our subjects is a way of protecting oneself from others (Frankenburg & Zanarini, 2006
The second finding concerns the relationship between cBMI and functional outcome. In previous reports, we have shown that overall the psychosocial functioning of our subjects has improved somewhat over time, particularly in those subjects who experienced a symptomatic remission (Zanarini, Frankenburg, Hennen, Reich, & Silk, 2005
). We now show the relationship between psychosocial functioning and changes in cBMI. As noted above, there was a significant relationship between increases in cBMI and subjects reporting having no partner. Just under half of our subjects reported having no partner, illustrating the difficulty our subjects have in initiating or maintaining intimate relationships. The chances of forming an intimate relationship were lower with increasing cBMI. This is consistent with findings in the general population, where researchers have found that obese women are less likely to marry than are women of normal weight (Enzi, 1994
Our subjects with increasing BMI are more at risk of reporting a poor school or work history, receiving disability, receiving a GAF score of 60 or less, and reporting a low income.
The relationship between increasing cBMI and functional outcome as represented by income is well known. Researchers in Finland found that obese women (but not obese men) had significantly lower income than non-obese women (Sarlio-Lähteenkorva, 2004
). The relationship is probably complex, bi-directional and self-reinforcing. Our subjects have poor school or work records. This may be caused in part by discrimination against the obese (Puhl & Brownell, 2001
). Obesity itself, even among fairly young people, can be associated with medical problems leading to disability (Lakdawalla, 2004
). Either of these conditions, doing poorly at work or being on disability, leads to a low income, which in itself can be associated with obesity. One reason for low income leading to obesity may be the easy availability of cheap fast food, which is high in saturated fats and calories and low in satiety value (Pereier et al., 2005).
The third finding is unsurprising. Our subjects who had an increase in their weight over time suffered more medical illnesses. They also had more medical emergency room visits and medical hospitalizations, which represent expensive forms of medical treatment. This finding confirms earlier work (Frankenburg & Zanarini, 2004
) and emphasizes the importance of normal weight in maintaining somatic health among the population with borderline personality disorder.
Although a full discussion of the relationship between obesity and affective disorders and stress is beyond the scope of this manuscript, it is important to note that there is a well described but complex connection between mood disorders and obesity, possibly mediated through perturbations of the hypothalamic-pituitary-adrenal axis, which is central to the stress response. Changes in insulin resistance, also a well-known feature of obesity, may activate immune-inflammatory networks involved with both affective symptoms and vascular pathology (McIntyre et al., 2009
Obesity is of particular importance with respect to women and the risk of developing metabolic syndrome. This syndrome is an ill defined cluster of the following: abdominal obesity, hypertension, insulin resistance, hypertriglyceridemia, low HDL cholesterol, elevated fasting blood glucose, hypercholesterolemia, proinflammatory markers and prothrombotic state. Metabolic syndrome significantly increases the risk of developing diabetes, heart disease, and/or stroke. In young women (but not men) the risk of developing metabolic syndrome doubles coincident with depression (Kinder, Carnethon, Palaniappan, King, & Fortmann, 2004
). Women who are treated with atypical antipsychotic medication are at greater risk of developing metabolic syndrome than are men (McEvoy et al., 2005
Our study has some limitations. First, our data were obtained by self-report. With respect to accurate reporting of weight and height, validation studies have found that overweight subjects may underestimate their weight, while all subjects overestimate their height (Mokdad et al., 2003
). Therefore our results may err on the conservative side when it comes to estimating BMI. However, many studies reporting on BMI in psychiatry use self-reported data (Petry, Barry, Pietrzak, & Wagner, 2008
The second limitation to our study is that we did not use abdominal circumference as a measure of obesity. Excess abdominal adiposity, captured by the waist-to-hip ratio or a measurement of the waist circumference, is in itself a risk factor for metabolic problems (Fox et al., 2007
) and depression (Lee, Kim, Beck, Lee, & Oh, 2005
). However, in practice, obtaining a valid abdominal circumference can be difficult, and many epidemiological studies continue to rely on the BMI.
The third limitation is that all BPD subjects were inpatients at baseline and people with BPD who have never been hospitalized may differ from these subjects in their BMI, their outcomes, or both.
The fourth limitation is that for some of our subjects who were underweight at their index admission, an increase in cBMI is actually a marker of health. However, obesity is more common in our subjects than is underweight. Therefore our findings are conservative, and if they err, they err by underestimating the seriousness of increasing BMI in female borderline subjects who were not underweight at the beginning of this study.
The fifth limitation is that we are only reporting on our female subjects. This is because BMI is perceived quite differently in males than in females. Indeed for males an increase in weight is actually associated with less depression and suicidality (Mukamal, 2007
; Palinkas, Wingard, & Barrett-Connor, 1996
). Moreover, as noted above, the interlocking relationships between psychiatric illnesses, psychotropic medications, and BMI are different in women than they are in men.
Despite these limitations, our study has important clinical implications. Long-term programs to monitor and treat weight gain in this vulnerable population are needed. Mental health providers are well positioned to identify overweight and obese patients and to identify possible modifiable risk factors, such as polypharmacy, unhealthy eating habits, and lack of exercise (Frankenburg & Zanarini, 2006
). For some patients excessive body weight may play a protective role, albeit one that comes at a high cost.
More studies that assess changes in BMI in borderline patients (female and male) are needed. Examination of the roles that psychotropic medications, stress, severity of affective disturbance, and level of physical activity play in the maintenance of body weight will be helpful. The medical consequences and costs of excess weight in BPD will be important to follow. As our subjects move into middle age, we suspect that the contribution of excess weight to medical illnesses will increase.
In conclusion, this is the first prospective long-term study of cBMI in well-described female borderline patients in which the relationship with symptomatic, functional, and medical outcomes was studied. The long-term implications of increasing BMI in this group of patients are serious and include disadvantages in all of these areas. The findings show the utility of measures of the duration of risk exposure for both life-course studies of health and tests of cumulative-disadvantage theory.
In this paper we have highlighted the importance of overweight and obesity in the female BPD population. Future work is needed to develop and implement obesity prevention and treatment strategies to determine if these need to be specific to BPD.