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Implications for Treatment and Prognosis of Borderline and Substance Use Disorders

Implications for Treatment and Prognosis of Borderline and Substance Use Disorders

Borderline personality disorder (BPD) is a severe disorder characterized by a pervasive pattern of instability in the regulation of emotion, interpersonal relationships, self-image, and impulse control. Approximately 2% of the general population meet criteria for BPD.1 In psychiatric treatment settings, prevalence rates for BPD are considerably higher, with rates of 8% for outpatients and 15% for inpatients.2 An estimated 3% to 10% of persons with BPD commit suicide.3 The disorder constitutes a significant social and economic burden on family resources and health care systems since it is associated with severe functional impairment and high rates of treatment utilization.

BPD and substance use disorder (SUD) often co-occur. Comorbid BPD and SUD is related to a variety of severe adverse outcomes, including participation in the sex trade; a large number of sexual partners; needle sharing; polysubstance use; more frequent and more serious drug overdoses; increased risk of suicide attempts; and more severe psychiatric, family, and legal problems.4-12 BPD has also been found to complicate the treatment of SUD.13-15 This article provides an overview of the prevalence of co-occurring BPD and SUD, neurobiologic hypotheses for the link between BPD and SUD, and treatment options that have proved effective for persons with comorbid BPD and SUD.

BPD and SUD comorbidity
Apart from antisocial personality disorder, BPD is probably the most common personality disorder in persons with SUD. Nearly one third of those with
a lifetime SUD diagnosis also have BPD (median, 27%; range, 5.2% to 74.0%).16,20 BPD appears to be less prevalent in persons with alcohol use disorders (median, 16%; range, 3.2% to 27.4%) than in those with drug use disorders, especially cocaine and opioid abuse.17,20 For example, Ross and colleagues17 found that almost half (47%) of individuals using heroin who entered treatment for SUD also had BPD. Note that the prevalence of BPD in this sample is far higher than that reported in other studies. Diagnostic discrepancies across studies examining the rates of comorbidity in persons with SUD are probably due to confounding methodologic factors, including the use of different assessment instruments, variable evaluator training, and differing sample characteristics (eg, treatment-seeking vs nontreatment-seeking). Women with SUD are more likely to have BPD than men.17,20

Conversely, more than half of those who have BPD also have a lifetime SUD diagnosis (median, 56.5%; range, 22.7% to 86%).20-22 Alcohol use disorders tend to be slightly more common in those with BPD (median, 48.9%; range, 21% to 100%) than in those with drug use disorders (median, 43.1%; range, 19% to 76%).20,21,23 Comorbidity rates have not always been reported separately for men and women, but in a study by Zanarini and colleagues,21 the researchers found that male psychiatric patients with BPD were more likely to have SUD (81.9%) than their female counterparts (59.1%)

Explanations for the association
There are several explanations for the strong association between BPD and SUD. First, the core BPD traits (affect dysregulation, impulse dyscontrol) are known to predispose patients to SUD and to affect the severity of substance use. Second, BPD and SUD have common familial precursors, such as family history of SUD and antisocial personality disorder,24 child abuse, and neglect. Finally, core dimensions of BPD appear to have a neurobiologic cause,25-27 most saliently evidenced as prefrontal cortex (PFC) dysfunction, which is also implicated in the development of SUD.28,29

Neurobiologic hypotheses
Imaging research, both MRI and positron emission tomography (PET), offers evidence that neurologic dysfunction is at the root of the affective and behavioral dysregulation intrinsic to BPD. Structural studies using MRI have demonstrated volume loss in the hippocampus and/or amygdala in women with BPD more than in healthy controls.30-33 These findings have been related to histories of childhood abuse, with the volume loss related to severity of childhood trauma.34

Additional evidence stems from investigations measuring the metabolic function of the brain using PET technologies. For example, prefrontal hypometabolism and diminished metabolic response to serotonergic activation in areas of the PFC have been found in PET studies of persons who have BPD (and other impulsive personality disorders).35-39 The affected areas include the orbitofrontal and ventromedial regions that are important in the regulation of affect and impulse. Damage to this area of the brain results in a syndrome of disinhibited, socially inappropriate, impulsive, and aggressive behavior.

Functional MRI studies in BPD have demonstrated abnormal responses to social cues (such as face recognition) in the amygdala, which increases the likelihood of inappropriate emotional and behavioral responding.40,41 Taken together, these findings suggest that some symptoms of BPD may be mediated in part by a disorder in serotonergic regulation and the prefrontal and limbic dysfunction that results in impaired inhibitory control.

A large body of evidence implicating PFC dysfunction is also seen in the literature on neuropsychology.25-27 Using tests of cognitive capacity and efficiency that are sensitive to and validated for detecting lateralized and localized cortical dysfunction, many studies have observed a pattern of impairment in PFC function. Dysfunction in PFC is associated with a variety of cognitive impairments subsumed within the rubric of executive cognitive functioning capacity. These functions include, but are not limited to, strategic planning, flexible problem solving, attention control/ working memory, self-monitoring goal-directed behavior, and cognitive control over emotion and behavior. Low executive cognitive functioning capacity is commonly manifested by impulsivity, labile emotion, distractibility, and aggression following minimal provocation. These are core characteristics of BPD and play a significant role in SUD.

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