Predicting specific trends over the next 20 years is highly uncertain and dependent on various factors such as changes in diagnostic criteria, mental health awareness, treatment availability, and societal developments.
Cluster B personality disorders include disorders such as Borderline Personality Disorder, Narcissistic Personality Disorder, Histrionic Personality Disorder, and Antisocial Personality Disorder. The prevalence of these disorders may be influenced by several factors, including changes in mental health diagnoses, awareness, and the implementation of interventions.
However, it's important to approach such predictions with caution as mental health is a complex area, and predicting population changes for specific disorders can be challenging. Societal attitudes toward mental health and the availability of mental health services can also significantly impact diagnosis and treatment rates.
To get more accurate and up-to-date information on this topic, it's best to refer to recent studies and reports from reputable sources and mental health organizations.