Distinguishing comorbidities from differential diagnoses in bipolar disorder

Before you treat a patient with bipolar-I disorder (BD-I), you need to know what you are treating, including all patient and history factors — a phenomenological description precedes treatment, said Professor Goldberg.

Distinguish comorbidities from differential diagnoses

Most patients with bipolar disorder have at least one comorbid psychiatric disorder

A careful clinical interview, longitudinal history and collateral historians are essential to make an accurate diagnosis of BD-I and enable the correct treatment, he explained. The challenges include:

• the overlap of symptoms with those of the differential diagnoses — an online survey of 154 psychiatrists revealed that 36%, 31%, 20%, and 13% found it most difficult to differentiate BPD, MDD, ADHD, and schizophrenia from BD-I, respectively¹
• the presence of comorbid psychiatric disorders — a study of 288 patients with BD-I, revealed that 65%, 42%, and 24% had one, two, or three comorbid psychiatric disorders, respectively — most commonly anxiety and substance use disorders, and to a lesser extent, eating disorders²

Comorbidity is associated with an earlier age of BD-I onset and a worsening course of BD-I.²

Is the diagnosis BD-I or BD-I with comorbid BPD and/or PTSD?

Approximately 20% of people with BD-I have comorbid BPD³ and from 4% to 40% have comorbid PTSD,⁴ resulting in a complex diagnostic territory, said Professor Goldberg.

Bipolar disorder with comorbid PTSD is often associated with substance use disorder

Strategies to help determine whether or not the disorders are comorbid include:

• a focus on overlapping and non-overlapping symptoms, for instance changes in sleep and energy can help clarifying a diagnosis of BD-I — excessive energy is a fundamental defining feature of BD-I and drives impulsive decision-making

• distinguishing identifiable episodes from persistent trait characteristics by analyzing the baseline from which they deviate — there should be apparent on-off highs that may last weeks in BD-I
• identifying interpersonal or environmental triggers, such as sleep deprivation and crossing time zones
• recognizing that a history of trauma can complicate the course across all diagnoses

BD-I with comorbid PTSD is more common in women than in men and in BD-I than in BD-II, noted Professor Goldberg. Key features include shorter durations of euthymia, an increased risk for mood episode relapse, a higher depressive symptom burden, a poorer quality of life and a higher prevalence of comorbid substance use disorder.³

Different patterns of affective instability occur in BD-II and BPD, with more depression and euphoria in BD-II and more anger in BPD.⁵ 

Is the diagnosis BD-II depression or MDD with comorbid BPD?

A variety of clinical features help in differentiating BD-II depression from MDD with comorbid BPD.

MDD comorbid with BPD is more often associated with PTSD than BD-II depression

A study of 206 patients with MDD with comorbid BPD and 62 patients with BD-II depression without BPD revealed that patients with MDD with comorbid BPD were significantly more often diagnosed with:

• PTSD (p<0.001)
• a substance use disorder (p<0.01)
• somatoform disorder (p<0.05)
• other nonborderline personality disorder (p<0.05).

Clinical ratings of anger, anxiety, paranoid ideation and somatization were significantly higher in the MDD with comorbid BPD group compared with the BD-II group and the MDD with comorbid BPD group made significantly more suicide attempts (all p<0.01).