Psychological Disorders for the MCAT: Everything You Need to Know
/Learn key MCAT concepts about psychological disorders, plus practice questions and answers
(Note: This guide is part of our MCAT Psychology and Sociology series .)
Part 1: Introduction to psychological disorders
Part 2: Psychotic, depressive, and related disorders
a) Schizophrenia
b) Depressive disorders
c) Bipolar disorders
d) Personality disorders
e) Somatic symptom disorders
Part 3: Behavioral and related disorders
a) Obsessive-compulsive disorder
b) Body dysmorphic and eating disorders
c) Post-traumatic stress disorder
d) Anxiety disorders
e) Dissociative disorders
Part 4: Additional neurological disorders
a) Aphasia
b) Parkinson’s disease
c) Alzheimer’s disease
Part 5: High-yield terms
Part 6: Passage-based questions and answers
Part 7: Standalone questions and answers
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Part 1: Introduction to psychological disorders
Psychological disorders are a characteristic set of feelings, thoughts, or behaviors that differ from the cultural norm and can cause distress to the individual suffering from them.
The Diagnostic and Statistical Manual of Mental Disorders (DSM) is a standardized resource used to assist clinicians in classifying and diagnosing these disorders. There are 20 different classes of psychological disorders defined by the DSM. In recent decades, we have learned a great amount about the physiology of these disorders and are able to classify them with increasing specificity. Within this guide, we’ll go over several key types of psychological disorders, their biological basis, and much more.
It may also be helpful to keep in mind the biomedical and biopsychosocial approaches to treatment. These are frameworks, or perspectives, used to guide professional therapies and treatment for a psychological disorder.
The biomedical approach views the root of these disorders as a physiological imbalance or disturbance. If this is true, then the method of treatment should also be biomedical in nature, aiming to reduce the symptoms of the disorder through a strictly scientific, neurochemical approach. This is a much more narrow scope of approach than the biopsychosocial approach because this approach fails to focus on additional stressors and factors in an individual’s life that may contribute to or exacerbate the disorder. For instance, an anxiety disorder could be due to neurotransmitter imbalance within emotional regions of the brain (a biomedical explanation) but could also be due to patterns of neglect in a family (an environmental factor).
The biopsychosocial approach is a more holistic view of psychological disorders. This approach considers biomedical, psychological, and social factors when considering stressors that may exacerbate the disorder. As you may have presumed, biomedical factors refer to an individual’s physiology; psychological factors refer to their thoughts and emotions; and social factors come from environmental, societal factors that are beyond the individual’s control. Under this framework, biopsychosocial treatment may combine direct therapy with a patient (such as prescribing medication or through one-on-one therapeutic sessions) and indirect therapy, which provides support for the individual with help from family, friends, or other components of the individual’s social network.
This is a high-yield topic for the MCAT. Let’s begin!
Part 2: Psychotic, depressive, and related disorders
Many psychological disorders appear to be somewhat hereditary or genetic. We will first address some of these disorders, starting with the psychotic disorders.
a) Schizophrenia
Individuals who suffer from psychotic disorders suffer from psychosis. Psychosis can manifest in feelings of paranoia, delusions, hallucinations, and a general loss of reality.
While the DSM lists several forms of psychotic disorders, the MCAT will focus on schizophrenia as the representative psychotic disorder. Schizophrenia is characterized by the presence of several positive symptoms that characterize psychosis, along with negative symptoms that further illustrate a deviation from normal behavior.
The prodromal phase, or prodrome, is a period of time directly before a diagnosis of schizophrenia. As this phase is primarily characterized by an abrupt change in behavior, family members and friends may notice “odd” behavior for a period of weeks or months, including a withdrawal from typical social activities and mood swings. The end of prodrome is marked by the onset of positive and negative symptoms of schizophrenia.
Positive symptoms refer to behaviors or thoughts that are exhibited in addition to an individual’s normal behavior, such as delusions, hallucinations, or nervous tics.
Positive symptoms come in many shapes and sizes. These behaviors are considered “symptoms” because they differ from the social norm of the culture in which they are observed. Hallucinations or delusions, for example, are considered commonplace in some Caribbean cultures as part of rituals, but in western culture, these may seem like symptoms.
Hallucinations are false observations that are not based on reality but are perceived as such. These can be auditory, like voices in someone’s head, or visual, like seeing a dead relative. Auditory hallucinations are more common than visual.
Delusions are held beliefs that directly contradict what is observed in reality. Delusions are usually firmly held onto by an individual and are generally not shared with multiple people.
Individuals may also begin to exhibit disorganized thoughts and behaviors. Patients with disorganized thought may be unable to express a cohesive narrative in conversation and instead express haphazard thoughts. Word salad is an extreme example of this, when the expressed thoughts are simply random words strung together. Disorganized behaviors follow a similar theme and refer to when an individual is unable to carry out their normal routine.
Negative symptoms refer to the lack or absence of an individual’s normal behavior, like the inability to eat or lack of emotion (or lack of affect). Affect refers to the display and conveying of emotion. Someone with flat affect displays virtually no emotion at all, while someone with inappropriate affect displays affect that is discordant with the individual’s speech or behavior.
Schizophrenia is also often associated with the downward drift hypothesis, stating that the symptoms of schizophrenia can lead to a decline in social wealth and resources, putting the individual at greater risk for experiencing worsening social factors and increasing the intensity of symptoms. This leads to a vicious cycle of worsening schizophrenia and socioeconomic status.
Based on genetic studies, the onset of schizophrenia seems to have a high hereditary factor. On a neurotransmitter level, individuals with schizophrenia appear to have elevated levels of dopamine in the brain. Neuroleptics (dopamine receptor antagonists) are used to treat schizophrenia.
b) Depressive disorders
While mood swings and natural sadness may last for hours or days, depressive disorders are characterized by an abnormally long period of sadness or intense feeling. Major depressive disorder is a mood disorder and is characterized by at least one major depressive episode. To be diagnosed with a major depressive episode, the patient must experience feelings of depression or sadness for at least two weeks and experience at least five symptoms from the following list:
low or depressed mood
anhedonia (loss of interest in previously interesting activities)
changes in appetite and weight gain or loss
sleep disturbances
persistent feelings of guilt
difficulty concentrating
thoughts of death or suicide
decreased energy in day-to-day activity
Depression is highly associated with an overactive amygdala: a small structure within the brain that controls basal emotions, such as fear and anxiety. The monoamine theory of depression describes a key physiological feature associated with depression: decreased levels of the neurotransmitters serotonin, dopamine, and norepinephrine levels.
Patients who experience depressed mood that is not severe enough to be diagnosed as a major depressive disorder may be diagnosed with dysthymia. Dysthymia is often diagnosed in individuals who experience a depressed and low mood for at least 2 years but who do not experience other symptoms of major depressive disorder.
Seasonal affective disorder (SAD) is not an isolated diagnosis in the DSM. Individuals who do not experience major depressive disorder or dysthymia may still experience a persistent depressive mood during the winter months. It is hypothesized that the lack of sunlight during the winter causes disruptions in melatonin metabolism, thereby affecting mood. As a result, bright light therapy is typically prescribed as a therapeutic method.
c) Bipolar disorders
Bipolar disorders are characterized by some combination of manic episodes (or hypomania) and depressive episodes.
Manic episodes are periods characterized by intensely high energy, high productivity, decreased need for sleep, and/or thoughts of grandeur. These episodes of elevated mood must last more than one week. Similarly, hypomania is an increased level of excitability; however, it is distinguished from mania as it does not inhibit the individual’s normal routines to the same degree. Depressive episodes will manifest similarly to the symptoms listed in the depressive disorders, with periods of persistent low mood and anhedonia.
There are three forms of bipolar disorder, each characterized by manic and depressive episodes occurring to differing degrees.
A diagnosis of bipolar I disorder requires documented manic episodes but may or may not require depressive episodes.
A diagnosis of bipolar II disorder requires documented hypomania, with at least one major depressive episode.
A diagnosis of cyclothymia requires a combination of hypomanic episodes and periods of dysthymia. Note that these periods of hypomania and dysthymia do not need to be as intense as periods of mania or depression.
Bipolar I disorder, bipolar II disorder, and cyclothymia all involve differing degrees of mania and depression.
The monoamine/catecholamine theory of depression explains the origin of mania and depression from a neurological transmitter. Under this theory, an overabundance or paucity of norepinephrine and serotonin leads to mania and depression, respectively.
d) Personality disorders
Personality disorders manifest in behavior patterns that appear to be erratic or strange by cultural standards. These disorders tend to warp the individual’s emotions, interpersonal functioning, and cognition in a way that results in impulsive actions and faulty explanations. Importantly, individuals with personality disorders tend to consider their behaviors and thoughts to be completely normal! They do not necessarily recognize these erratic thoughts and behaviors as abnormal or distressing.
While there are many subtypes of personality disorders, they are generally clustered into three overlapping groups. For the MCAT, it will be sufficient to distinguish disorders as belonging to Cluster A, Cluster B, or Cluster C.
Cluster A disorders include paranoid, schizotypal, and schizoid personality disorders. Paranoid personality disorder leads individuals to have a very strong distrust of others and their motives. Schizotypal personality disorders are characterized by eccentric thinking unaccepted by the cultural norm. Schizoid personality disorder applies to individuals who are disinterested in or detached from personal relationships with others. This cluster may be well-remembered as the “weird” disorders.
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