Text adapted from: "The adult patient with a personality disorder," in Psychiatry in primary care by Michael Rosenbluth, Matthew Boyle & Lucille Schiffman (CAMH, 2019).
When There is an Axis-1 Disorder
It is important to identify the comorbid Axis I diagnosis and treat it robustly with the appropriate medication. If there is a comorbid personality disorder, the main pharmacotherapy adjustment is to consider the toxicity of large amounts of medication because patients with Borderline Personality Disorder (BPD) are at risk for overdose.
Using lithium for comorbid bipolar disorder and borderline personality disorder (BPD) is somewhat controversial. Several good studies demonstrate that lithium for patients with bipolar disorder without comorbid personality disorder can reduce suicidal behaviours and completed suicide (Baldessarini et al., 2006; Cipriani et al., 2005). However, there is no research about suicide and lithium use in patients with comorbid BPD and bipolar disorder. This is important because lithium has a narrow therapeutic range regarding lethal overdose.
Estimates of the comorbidity of bipolar disorder and borderline personality disorder vary widely, from 9 per cent to 28 per cent (Gunderson et al., 2006; Rosenbluth et al., 2012; Zanarini et al., 2004). Diagnosing co-occurring bipolar disorder is important because modifications in pharmacotherapy (e.g., using atypical antipsychotics instead of lithium) will be required for those patients.
When using medication, it is preferable to target identifiable comorbid Axis I diagnoses and use the appropriate medication indicated. However, when clear-cut comorbid Axis I diagnoses are not present, you can sometimes consider medications for target symptoms, for example, the tendency to have brief psychotic reactions or to be emotionally labile (Rosenbluth et al., 2012). Atypical antipsychotics have sometimes been seen as ego or brain “glue”, making these patients less sensitive to the characteristic meltdowns they are prone to.
In general, there is limited evidence that any drug treatment improves symptoms of borderline personality disorder (BPD) or its overall severity. Recent studies have failed to demonstrate a contribution for pharmacotherapy in targeting BPD, for example, the mood-stabilizing medication lamotrigine (Crawford et al., 2018).
However, a variety of pharmacotherapies, most often mood stabilizers and second-generation (atypical) antipsychotics (SGAs), are used to treat core symptoms of borderline personality disorder. While SGAs have been used due to their expected stabilizing effect on cognitive–perceptual symptoms, mood, anxiety, impulsivity and aggression (Herpertz, 2007), several literature reviews found insufficient high-quality evidence to recommend an SGA for managing these symptoms in BPD (Wasylyshen & Williams, 2016).
Mood stabilizers are often used in borderline personality disorder to treat impulsive–behavioural dyscontrol symptoms and affective dysregulation. Historically, they have been encouraged because of the idea that borderline personality disorder is related to bipolar spectrum disorder (Gunderson & Choi-Kain, 2018). However, these disorders are separate entities, and the co-occurrence of borderline personality disorder and bipolar I or II disorder is less than 30 per cent (Gunderson et al., 2014). Recent studies have demonstrated that lamotrigine is not an effective primary treatment for core symptoms of borderline personality disorder (Crawford et al., 2018).
Although there is no medication that improves core symptoms, several medications have shown promise in treating comorbidities of borderline personality disorder. A recent review recommended that, of the antidepressants, monoamine oxidase inhibitors (MAOIs) and fluvoxamine might offer the best therapeutic effect on mood and anxiety (Ripoll, 2013).
Three randomized controlled trials found that supplementation with omega-3 fatty acids, both with and without other psychotropic medications, was effective in treating BPD core symptoms (Bozzatello et al., 2016).
To date, no psychotropic medications have been proven to be effective in treating borderline personality disorder overall, so targeted and short-term use of medications for specific comorbid symptoms is recommended to minimize side-effects.