Personality Disorders: What Are Cluster C Personality Disorders?

Understanding Cluster C Personality Disorders

While borderline, narcissistic, and antisocial personality disorders are among the most well-known and frequently discussed personality disorders, the most common personality disorder in the United States is actually obsessive-compulsive personality disorder (OCPD).

Obsessive-compulsive personality disorder is one of the three “Cluster C” personality disorders listed in the Diagnostic and Statistical Manual of Mental Disorders (DSM), the primary reference text for mental health professionals. These disorders manifest differently but have features in common and are treated in similar ways.

What Are Cluster C Personality Disorders?

Personality disorders are mental health conditions that are established by late adolescence or early adulthood. They are caused by a combination of genetic, biological, and environmental factors that affect a person in infancy, childhood, and early adolescence. They are expressed more as aspects of identity than as symptoms of a transient condition, though advances in clinical insight show they respond to treatment and can even go into remission.

There are three different categories, or clusters, of personality disorders listed in the DSM: Cluster A, Cluster B, and Cluster C. The Cluster C disorders are anxious personality styles that include the following three disorders:

  • Avoidant Personality Disorder
  • Dependent Personality Disorder
  • Obsessive-Compulsive Personality Disorder

In general, Cluster C or anxious personality disorders are caused by an anxious temperament and childhood experiences that reinforce certain fears.

People with avoidant personality disorder (APD) exhibit a pattern of avoiding social activities, including occupational activities that require significant interpersonal interaction. They do this not out of an enjoyment of solitude, but fear that others will judge or dislike them or find them inadequate. They often have experiences of being humiliated or socially rejected as children.

People with dependent personality disorder (DPD) believe they need others to take care of them and act accordingly. They seek excessive reassurance and advice before engaging in an activity, ask others to take responsibility for them, and have difficulty asserting themselves or doing tasks independently. They do this not because they enjoy close collaboration, but out of fear that they cannot be alone without a significant risk of harm. They often had overprotective parents who prevented them from making independent decisions.

People with OCPD have a rigid and perfectionistic personality style and focus excessively on rules and details. They are often unable to complete tasks, spending hours trying to get perfect results and giving up when they can’t. They frequently become “workaholics” who focus on work to the exclusion of all else. They do not like working with others and prefer to control and complete all aspects of an activity on their own. They do this not out of enjoyment of precision, but fear that they cannot trust or rely on others or society in general. They often grew up with rigid parents who criticized or punished them for imperfect performance on tasks.

Cluster C Personality Disorders and Anxiety Disorders

The Cluster C personality disorders all share features in common with anxiety disorders including social anxiety disorder (SAD) and obsessive-compulsive disorder (OCD). It is not always easy to distinguish Cluster C personality disorders from related anxiety disorders, but there are some ways to tell the difference.

The main way to tell them apart is to assess how pervasive symptoms are and how strongly identified a person is with them. For example, a person with SAD is more likely to recognize that their social fears are irrational, while someone with APD is more likely to believe there is something deeply wrong with them.

While personality disorders are generally more severe in their impact, they may initially seem less severe because of their stability over time. Behaviors related to personality disorders are more likely to be consistent over long periods, or even a lifetime, while symptoms of an anxiety disorder are more likely to arise as a marked difference in functioning from before.

For example, someone with OCPD is more likely to have established a way of working that is rigid and perfectionistic, while someone with OCD is more likely to exhibit the overt repetitive or compulsive behaviors associated with that disorder. In general, OCD has acute effects that arise in specific contexts while OCPD has more pervasive effects that characterize an approach to nearly all activities.

Treatment for Cluster C Personality Disorders

In general, medication is not the primary treatment for personality disorders. In the case of Cluster C personality disorders, however, anti-anxiety medications are sometimes prescribed, especially selective serotonin reuptake inhibitors (SSRI) such as fluoxetine (Prozac), paroxetine (Paxil), and sertraline (Zoloft).

These can reduce anxiety but cannot resolve the underlying personality factors behind it. Research shows that personality disorders respond less well to SSRIs than related anxiety disorders. They are often used for Cluster C personality disorders only when severe anxiety symptoms limit a person’s ability to participate in or make progress in therapy.

Like anxiety disorders, Cluster C personality disorders are driven by cognition, primarily beliefs about the self and others. For this reason, they all respond well to cognitive behavioral therapy (CBT). A therapist who provides CBT helps clients identify irrational beliefs or distorted thought patterns, challenge them, and ultimately change them. A review of a wide range of research shows that CBT improves functioning and reduces symptoms of Cluster C personality disorders.

In CBT, a therapist can help someone with APD challenge distorted beliefs about their social incapacity or unworthiness. They might encourage someone with DPD to explore if they are truly incapable of acting independently, perhaps giving them behavioral “homework” to try completing small tasks on their own. Beliefs about the consequences of imperfect performance on tasks might be the target for a client with OCPD.

Acceptance and commitment therapy (ACT) also encourages people to identify thoughts that drive distressing emotions and behavior. However, instead of having people label thoughts as “false” and try to change them, therapists who practice ACT help clients learn how to accept them without acting on them and to take actions that reflect personal values. Research shows ACT is just as effective as CBT in the treatment of anxiety disorders and is likely to be just as effective in treating anxiety-based personality disorders.

Cluster C Personality Disorders and Addiction

Like people with anxiety disorders, research shows that people with Cluster C personality disorders use alcohol more frequently than other substances. This may be due to the social acceptance of alcohol or its efficacy in relieving anxiety, especially social anxiety. However, people with these personality disorders can become addicted to any substance that helps them feel less anxiety and shame. It’s important for people with co-occurring disorders to receive treatment that addresses both conditions to prevent relapse and promote deeper recovery.

Group interventions are common in substance abuse treatment and can be particularly helpful for people with co-occurring anxiety or Cluster C personality disorders. Groups are not only a way to provide targeted behavioral health interventions but can act as a form of exposure therapy for people with social anxiety. They are living laboratories where people can examine and challenge beliefs about whether they are able to connect to other people, be rewarded for independent insight, and be accepted in spite of their imperfections.


Cluster C personality disorders are expressions of self that reflect an adaptation to long-term anxiety. They limit people in ways that are painful and distressing for them and that reinforce the perception that the world is hostile and that people can’t be trusted. Fortunately, with the right interventions, people with these conditions can start to change how they think and see the world and experience greater freedom and self-confidence.

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