DSM-5
The most recent fifth edition of the Diagnostic and Statistical Manual of Mental Disorders stresses that a personality disorder is an enduring and inflexible pattern of long duration leading to significant distress or impairment and is not due to use of substances or another medical condition. The DSM-5 lists personality disorders in the same way as other mental disorders, rather than on a separate axis, as previously.DSM-5 lists ten specific personality disorders: paranoid, schizoid, schizotypal, antisocial, borderline, histrionic, narcissistic, avoidant, dependent and obsessive–compulsive personality disorder. The DSM-5 also contains three diagnoses for personality patterns not matching these ten disorders, but nevertheless exhibit characteristics of a personality disorder:
Personality change due to another medical condition – personality disturbance due to the direct effects of a medical condition. Other specified personality disorder – general criteria for a personality disorder are met but fails to meet the criteria for a specific disorder, with the reason given. Unspecified personality disorder – general criteria for a personality disorder are met but the personality disorder is not included in the DSM-5 classification.These specific personality disorders are grouped into the following three clusters based on descriptive similarities:

Cluster A (odd or eccentric disorders)
Cluster A personality disorders are often associated with schizophrenia: in particular, schizotypal personality disorder shares some of its hallmark symptoms with schizophrenia, e.g., acute discomfort in close relationships, cognitive or perceptual distortions, and eccentricities of behavior. However, people diagnosed with odd-eccentric personality disorders tend to have a greater grasp on reality than those with schizophrenia.
There can be other factors such as problematic substance use or dependency or behavioral addictions. Therapists in this area can become disheartened by lack of initial progress, or by apparent progress that then leads to setbacks. Clients may be perceived as negative, rejecting, demanding, aggressive or manipulative. This has been looked at in terms of both therapist and client; in terms of social skills, coping efforts, defense mechanisms, or deliberate strategies; and in terms of moral judgments or the need to consider underlying motivations for specific behaviors or conflicts. The vulnerabilities of a client, and indeed a therapist, may become lost behind actual or apparent strength and resilience. It is commonly stated that there is always a need to maintain appropriate professional personal boundaries, while allowing for emotional expression and therapeutic relationships. However, there can be difficulty acknowledging the different worlds and views that both the client and therapist may live with. A therapist may assume that the kinds of relationships and ways of interacting that make them feel safe and comfortable have the same effect on clients. As an example of one extreme, people who may have been exposed to hostility, deceptiveness, rejection, aggression or abuse in their lives, may in some cases be made confused, intimidated or suspicious by presentations of warmth, intimacy or positivity. On the other hand, reassurance, openness and clear communication are usually helpful and needed.