Co-Occurrence of Borderline Personality Disorder and Bipolar Disorder
Bipolar Disorder is characterized by alternating periods (or episodes) of depressed mood with manic or hypomanic mood (elevated, expansive mood). Thus, bipolar mood swings from euphoric "highs," to depressed "lows," and looks very similar to the extreme mood changes observed in people diagnosed with Borderline Personality Disorder. The Borderline Personality Disorder is also characterized by significant problems with impulsivity. This characteristic impulsivity often leads to same risky behaviors that are frequently observed in someone with Bipolar Disorder during manic or hypomanic episodes: over-spending, shop-lifting, gambling, drug and alcohol use, and indiscriminate sexual liaisons. As a general guideline, the symptoms of Borderline Personality Disorder tend to occur in reaction to something that happened (such as an interpersonal conflict) and last for shorter periods of time, usually hours. In contrast, the depressed or manic moods of the Bipolar Disorder are not typically related to some identifiable life event and usually last much longer than a few hours (usually days or weeks). The difficult task of teasing apart these two diagnoses is best left to experienced professionals. In fact, these two disorders share so many similarities that some experts believe Borderline Personality Disorder could be a variant form of Bipolar Disorder. Often, the same medications are prescribed to treat both Bipolar Disorder and Borderline Personality Disorder.
Here are some other articles that discuss the relationship between Borderline Personality Disorder and Bipolar Disorder.
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Co-Occurrence of Personality Disorder and ADHD
A close relative of Bipolar Disorder is Attention Deficit/Hyperactivity Disorder (ADHD). Interestingly, ADHD is often associated with several personality disorders; namely the Cluster B disorders including Antisocial, Narcissistic, Histrionic, and Borderline Personality Disorders.
As the name implies, people with ADHD have a difficult time focusing their attention and staying on task. Their mind tends to wander and they abruptly change topics during conversations. They have a hard time structuring and scheduling themselves. In addition, if the person is fidgety and squirmy, having a hard time sitting still, and is always on the go, we speak of hyperactivity co-occurring with inattentiveness. Previously we have discussed the issue of impulsivity as it relates to personality disorders. Recall, impulsivity refers to a limited ability to control sudden impulses or urges to take some kind of immediate action without considering the consequences of those actions. In other words, there is an impaired ability to delay or inhibit the gratification of an impulse. The inattentive and hyperactive features of ADHD look very similar to the impulsivity characteristic of several personality disorders, particularly Cluster B (Antisocial, Narcissistic, Histrionic, and Borderline).
Several studies have shown that people who were diagnosed with ADHD in childhood were more likely than non-diagnosed peers to meet criteria for a personality disorder in adulthood. A study by Miller, Nigg, and Faraone (2007) found that adult ADHD co-occurs particularly often with Cluster B personality disorders (the dramatic, erratic, and emotional cluster) and Cluster C personality disorders (the anxious, fearful cluster). Given that impulsivity is a core feature shared by Cluster B personality disorders, and given that impulsivity along with thinking and concentration problems, can also be found in people with ADHD, it makes sense that these two conditions would frequently go together, or co-occur. The high co-occurrence between ADHD and Cluster C personality disorders might have to do with the relationship between anxiety and attention: it's very difficult to concentrate and focus when you're very anxious. However, we don't know why these disorders co-occur. More research is needed before we will understand the exact relationship between these disorders; for the moment, we can only speculate.
Here is some more information about the co-occurrence of personality disorders and ADHD.
Co-Occurrence of Avoidant Personality Disorder and Social Phobia
Social Phobia and Avoidant Personality Disorder are another pair of disorders that frequently co-occur. If you look at the definition of these two disorders, it is easy to see why this would be the case. Social Phobia is characterized by extreme anxiety in social situations that can take the form of a feeling of panic. Examples of these anxiety provoking social situations include talking to authority figures, attending parties, dating, and speaking or eating in front of other people. A person with Social Phobia is very afraid of embarrassment and is worried other people can tell how uncomfortable they are. Compare this to Avoidant Personality Disorder. A person with Avoidant Personality Disorder believes they are inferior. They are afraid that others won't like them, and consequently avoid social situations due to concerns they will be embarrassed, ridiculed, or rejected. You can see how these two disorders look very similar and would be hard to distinguish. Research has shown such a high rate of co-occurrence between these two disorders. In fact, many experts speculate they may be the same thing (Herbert, 2007).
Co-Occurrence of Schizotypal Personality Disorder and Schizophrenia
Another line of research, conducted mostly by the psychiatrists Larry Siever and Emil Coccaro (Coccaro and Siever, 2005), has investigated the relationship between Schizotypal Personality Disorder and Schizophrenia. These two disorders also seem to be very closely related. People with Schizotypal Personality Disorder come across as odd and eccentric. They tend to be very uncomfortable with other people, and often have only a few close relationships. Among the hallmark symptoms of Schizotypal Personality Disorder, are the symptoms that make this disorder appear very similar to Schizophrenia. Both disorders experience perceptual disturbances. In the case of Schizotypal Personality Disorder, patients report noticing flashes of light, or seeing objects or shadows only to realize that nothing is there. Additionally, people with Schizotypal Personality Disorder tend to be highly suspicious of other people. They often have odd or eccentric beliefs about the world that vary markedly from their cultural environment.
Schizophrenia is similarly characterized by difficulties with reality testing (i.e., distinguishing between what is real and what is not). Symptoms of Schizophrenia include seeing or hearing things that are not actually there, and delusions. Delusions are beliefs that are irrational or untrue. For instance, a person might have a paranoid delusion that someone has wire-tapped their phone and is out to harm them, even though this is not the case. They may also believe someone is controlling their thoughts or actions against their will. The thought processes in people with Schizophrenia are often jumbled up. Therefore, they may not make a lot of sense in a conversation. They often appear withdrawn and absent of any emotion.
Coccaro and Siever (2005) have identified biological and genetic commonalities shared by people diagnosed with Schizophrenia and Schizotypal Personality Disorders. Notably, close family members of people with Schizophrenia are at higher risk of developing Schizotypal Personality Disorder than are people who do not have diagnosed relatives (Coccaro & Siever, 2005). Brain imaging studies indicate that Schizophrenia and Schizotypal Personality Disorder share common structural deficits as well (Coccaro & Siever, 2005). Despite these similarities, people with Schizotypal Personality Disorder seem to be able to compensate for these deficits more readily than are people diagnosed with Schizophrenia. In general, Schizotypal Personality Disorder is milder and less disabling than Schizophrenia and is distinguished from Schizophrenia by more intact reality-testing. A borderline personality organization might be present (to use Kernberg's terms), but not the psychotic personality organization characteristic of Schizophrenia.