7.1 Understanding Psychological Disorders - Psychological Disorders

MCAT Behavioral Sciences Review - Kaplan Test Prep 2021–2022

7.1 Understanding Psychological Disorders
Psychological Disorders


After Chapter 7.1, you will be able to:

· Compare and contrast the biomedical and the biopsychosocial models of psychological disorders

· Recall the most common psychological disorders in the United States

Psychological disorders are characteristic sets of thoughts, feelings, or actions that cause noticeable distress to the sufferer, are considered deviant by the individual's culture, or cause maladaptive functioning in society, meaning that some aspect of the individual's behavior negatively impacts others or leads to self-defeating outcomes. Many disorders can be treated once diagnosed. The process of defining these disorders varies, and there are two main classification systems you’ll need to know for the MCAT.

Real World

Thomas Szasz, an outspoken critic of labeling people “mentally ill,” argues that most of the disorders treated by clinicians are not really illnesses. Rather, they are traits or behaviors that differ from the cultural norm. Szasz argues that labeling people as mentally ill is a way to force them to change and conform to societal norms rather than allowing them to attack the societal causes of their problems.


The first classification system to know for the MCAT is the biomedical approach to psychological disorders. Biomedical therapy emphasizes interventions that rally around symptom reduction of psychological disorders. In other words, this approach assumes that any disorder has roots in biomedical disturbances, and thus the solution should also be of a biomedical nature. This view is thought of as narrower than other approaches because it fails to take into account many of the other sources of disorders, such as lifestyle and socioeconomic status. For example, heart disease clearly has roots within the mechanisms of the cardiac muscle, but the causes of these malfunctions have as much to do with biomedical causes (such as genetics) as they do with lifestyle causes (such as a diet rich in salty, fatty foods; smoking; and alcohol use). Similarly, this biomedical approach can miss some underlying sources of psychological disorders and is often more effective when supplemented with a broader approach to diagnosis and treatment.

A broader classification system commonly used for these psychological disorders is the biopsychosocial approach. This method assumes that there are biological, psychological, and social components to an individual’s disorder. The biological component of a disorder is something in the body, like having a particular genetic syndrome. The psychological component of a disorder stems from the individual’s thoughts, emotions, or behaviors. Finally, the disorder’s social component results from the individual’s surroundings and can include issues of perceived class in society and even discrimination or stigmatization. All three of these aspects of a disorder are considered in the biopsychosocial approach for both diagnosis and treatment.

MCAT Expertise

The biopsychosocial model was originally theorized in a 1977 Science article and has grown in breadth, depth, and applicability since it was first described. In fact, the increased recognition of psychological and social factors on patient care was one of the primary drivers for the creation of the Psychological, Social, and Biological Foundations of Behavior section of the MCAT!

To better understand the biopsychosocial approach, consider depression. Certain genetic factors can make an individual more or less susceptible to depressive tendencies, showing a purely biological influence on the disorder. However, from a psychological perspective, the levels of stress that the individual experiences can also contribute to the severity of the depression experienced. Finally, the social environment may provide additional stressors or support from one’s career, family, and friends. Accordingly, in the biopsychosocial model, the goal is often to provide not only direct therapy—treatment that acts directly on the individual, such as medication or periodic meetings with a psychologist—but also indirect therapy, which aims to increase social support by educating and empowering family and friends of the affected individual.


To aid clinicians in considering these factors, the Diagnostic and Statistical Manual of Mental Disorders (DSM) was created. Originally, the manual was written to collect statistical data in the United States. It is now used as a diagnostic tool in the United States and various other countries. The manual is currently in its fifth edition, which was published in May 2013, so the common abbreviation seen is DSM-5. This manual is a compilation of many known psychological disorders. The DSM-5’s classification scheme is not based on theories of etiology (cause) or treatments of different disorders. Rather, it is based on descriptions of symptoms. It is used by clinicians to fit lists of compiled symptoms from a patient into a category and thus to diagnose that patient. The DSM-5 has 20 diagnostic classes of mental disorders; those that will be tested on the MCAT are discussed in this chapter.

Real World

David Rosenhan studied whether it was possible to be judged sane if you are in an “insane place” (a psychiatric hospital). Rosenhan and seven other “sane” people were admitted into psychiatric hospitals by reporting auditory hallucinations. Each of these pseudopatients was diagnosed to have either schizophrenia or bipolar disorder, and each was admitted. Once admitted, they acted completely normal—but it still took an average of three weeks to be discharged, and each was still given the diagnosis of schizophrenia in remission. Once labeled, it is very hard to distance oneself from the diagnosis of mental illness.


Suffering from a mental disorder can be a lonely experience because the disorder usually occurs only in the mind of the patient. However, the rates of these psychological disorders are higher than this experience would otherwise suggest. Table 7.1 covers these rates in detail.


Percentage Affected

Number Affected (in Millions)

Any mental disorder



Specific phobia



Social anxiety disorder



Major depressive disorder



Posttraumatic stress disorder



Bipolar disorder



Generalized anxiety disorder



Panic disorder



Borderline personality disorder



Obsessive—compulsive disorder






Anorexia nervosa






All cancers*






*Note: These nonpsychological conditions are included for comparison.

Table 7.1. One-Year Prevalence Rates for Psychological Disorders in the United States All data from this website: https://www.nimh.nih.gov/health/statistics/index.shtml

MCAT Expertise

The MCAT tests many, but not all, categories of mental disorder described within the DSM-5. Neurodevelopmental disorders, eating disorders, impulse control disorders, sleeping disorders, and others are not listed within the AAMC's guide to MCAT content, and as such are not included within this text.

MCAT Concept Check 7.1:

Before you move on, assess your understanding of the material with these questions.

1. What is the difference between the biomedical and biopsychosocial models of psychological disorders?

2. Name three psychological disorders with greater than 2% one-year prevalence in the United States (affecting more than 1 in 50 people per year). Refer to Table 7.1 if you get stuck.