Albert Ellis, the founder of Rational Emotive Behavior Therapy (REBT), suggests that negative thoughts in internalizing disorders often stem from irrational beliefs, particularly those categorized as "musturbatory" thinking, which are rigid, absolutist, and often unrealistic demands placed on oneself, others, or the world.
Ellis believed that the core of many internalizing disorders is a set of irrational beliefs that individuals hold about themselves and their environment. These beliefs are typically characterized by "shoulds," "oughts," and "musts," which can lead to negative thoughts and emotions when reality does not align with these strict and often unattainable standards.