Psychological Diagnostic Testing

How Can it Aid Diagnosis of Mental Disorders?


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What is Psychological Diagnostic Testing

Psychological diagnostic testing is a procedure used by psychologists that helps diagnose mental illness. It involves a series of assessments called psychological tests.

Psychological diagnostic tests measure the subject's intelligence, cognition, mental abilities, and behavior. They also help predict possible future outcomes of mental health. Studies have found that low childhood I.Q. increases the risk of mental illness later in life.1

Increasing Use of Psychological Tests for Non-Medical Purposes

The use of psychological diagnostic tests is not limited to hospitals or clinics. Such tests have become an integral part of the hiring process for businesses and the admission process for colleges. Schools and business firms use these tests to find out whether prospective students or employees are fit for the assigned tasks.

9 in 10 business firms use or plan on using psychological diagnostic tests while hiring employees. In the early 90s, about 20 million people in the U.S. took tests each year.2

Sales of psychological diagnostic tests increased from $250 million in 2001 to over $400 million in 2002.2 Psychological testing has now become a business worth billions of dollars.

What are the Uses of Psychological Diagnostic Testing?

Psychological diagnostic testing can be used to:

Help diagnose mental illness

Collect information about mental abilities, strengths, and weaknesses

Create a treatment plan

Assess personality, intelligence, and neuropsychological functioning

Determine whether a patient is eligible for a specific treatment

Who Provides Referrals for Psychological Diagnostic Testing?

Referrals for psychological diagnostic testing may come from:


Family physicians



Non-testing psychologists

Licensed mental health clinicians

Nurse practitioners

Reasons for a Referral

People may need psychological diagnostic testing if they have:

An unpleasant experience such as excessive fear

Symptoms of a mental illness such as depression

Bizarre behaviors that cause problems at school or in the workplace

Memory and attention problems

Severe mood swings

Feelings of hopelessness and extreme guilt

Personality changes

Fatigue and low energy levels

Recurrent suicidal thoughts or attempts

Psychological Diagnostic Test vs. Psychological Assessment

Many people use these terms interchangeably. However, they are not the same. Tests and assessments are two different tools used in a psychological evaluation.

A psychological diagnostic test is a part of psychological assessment.3 Psychologists use the tests to collect information about a patient's mental health status.

An assessment collects, integrates, and interprets information about a person with psychological issues. Its results show problems, capabilities, and individual traits. Assessments also help psychologists to design an effective treatment plan.

Psychological diagnostic tests measure one or more specific characteristics  — e.g., a memory test measures how a person memorizes particular information. A personality test determines individual personality traits. Extraversion, agreeableness, and conscientiousness are commonly tested personality traits.

The History of Psychological Testing

The history of psychological diagnostic testing dates back over 3,000 years in China. Chinese people used the tests to measure mental abilities, creative ideas, and visual perceptions.

Yet, it took a long time before psychological diagnostic testing began to flourish in the U.S. and Europe. The industrial revolution and World War II fueled the growth of such testing in the 20th century.

Below is a timeline of significant developments in psychology and psychological assessment.4, 5, 6


1890: American psychologist James McKeen Cattell first used the term "mental test." He was the first professor of psychology at the University of Pennsylvania. In 1988 he developed many tests to measure the mental functions of college students.7

1892: The American Psychological Association (APA) was founded. The APA regulates psychological research, education, and publication in the U.S.

Early 1900s

1905: French psychologist Alfred Binet developed an intelligence test for children called the Binet–Simon Scale. The test would later become the basis for what we call the "I.Q. test" today.

1916: The Stanford–Binet Intelligence Scale was published. This scale was a refined version of the Binet-Simon Scale.

1918: Hermann Rorschach developed the Rorschach Inkblot Method in which an examiner asks people to describe abstract images (inkblots). Their ways of describing the inkblots reveals their psychological types.


1930s: The use of intelligence tests soared in the U.S. because the U.S. had entered World War II. The U.S. government needed advanced tools to measure intelligence among its recruits.

1935: Christiana Morgan and Henry Murray published the Thematic Apperception Test (TAT). The TAT uses cards that have black and white drawings showing day-to-day life activities. The test-takers way of describing the cards yields information about their motivation and mental status. Today, the TAT is frequently used to diagnose psychological issues.

1939: David Wechsler introduced the Wechsler-Bellevue scale.8 This scale measures a person's intelligence, memory, and thought processes. It uses questions and nonverbal approaches, such as solving puzzles.

Current Era

Early 1970s: Theodore Millon developed several tools to measure personality traits and identify mental illnesses. Examiners started using computers to take tests and interpret the results.

1976: The International Test Commission (ITC) came into existence. The ITC played a crucial role in developing standards for the ethical use of psychological tests.

1988: The American Psychological Society was established. Now it is known as the Association for Psychological Science (APS). This non-profit organization informs the public about recent research findings in psychology.

What is a Psychologist?

According to the American Psychological Association (APA),

"A psychologist is an individual who is professionally trained in one or more branches or subfields of psychology."10

Psychologists have advanced degrees such as doctoral degrees in philosophy (Ph.D.), psychology (Psy.D.), or education (Ed.D.). They use talk therapy (psychotherapy) to help people with mental health problems.

They are trained in conducting mental health assessments, research, and organizational consultations. Some work in colleges or universities. Others work in hospitals or clinics. The military, the government, and business firms also employ psychologists.

Unlike psychiatrists, psychologists are not medical doctors. Thus, they are not allowed to prescribe drugs to treat psychiatric illness. Nonetheless, some states have given prescriptive authority to psychologists. These states are Iowa, Idaho, Illinois, New Mexico, and Louisiana.

What Types of Diagnostic Tests do Psychologists Use?

In psychological diagnostic testing, a psychologist may use:

Intelligence/Cognitive Tests to Check for Learning Disabilities

These assessments measure the ability to think, learn, and adapt to a new environment. Diseases, injuries, and mental illnesses can affect intelligence.

The most common cognitive tests are:

Montreal cognitive Assessment (MoCA)

Mini-Mental State Exam (MMSE)


Behavioral and Personality Tests

These tests help in diagnosing psychiatric disorders and planning treatment. Personality tests help describe a person's unique thoughts, attitudes, and behaviors.

Examples of personality tests are:



Minnesota Multiphasic Personality Inventory (MMPI)

The MMPI first became available in 1940. The revised version (MMPI-2) was published in 1989.11 This test measures a person's psychological state. It helps assess mental illnesses like depression, anxiety, and addiction.

Neuropsychological Tests

These tests check for issues due to neurological disorders and injuries to the brain. They are useful when a person shows signs of mental illness, but brain imaging tests show no abnormality. A neuropsychological test may be used to differentiate between dementia and depression.

An example of a neuropsychological test is the Clinical Dementia Rating (CDR), a 5-point scale that helps determine the severity of dementia by checking for symptoms that might suggest dementia or cognitive decline. These symptoms include problems with memory, judgment, orientation, and personal care. The examiner interviews the affected person and their family members to collect information. A score of 3 suggests severe dementia, and 0 indicates no dementia.12

Psychological Diagnostic Test Reports

After analyzing data from the tests, the psychologist prepares a psychological report. There are several formats for such reports. A typical report comprises the following sections:

Information about how the patient behaves and cooperates with the examiner

Description of mental abilities, strengths, and weaknesses

  • This may also include the symptoms of organic mental disorders

Results of the tests taken

Summary of the findings and recommendations for further care

What Do Psychological Diagnostic Tests Tell Psychologists?

Psychological diagnostic testing helps in the diagnosis of mental disorders. The psychologist analyzes the scores the patient has obtained in the tests. If they think the patient may have a mental health issue, they consult other health professionals.

Psychological disorders are hard to diagnose. Confirming a diagnosis often requires collaboration among health professionals.

In some cases, a psychological test alone may not be enough to confirm a diagnosis. Thus, a patient may need lab tests to measure their hormone levels and identify drug use behavior. Imaging tests may be necessary to rule out abnormalities in the brain or nerves.

Diagnosing Common Types of Mental Illness

Results from psychological diagnostic testing are useful in the diagnosis of:


Depression is more than normal sadness. It causes prolonged periods of grief, hopelessness, and helplessness. Depression is one of the leading causes of suicide. Each year, 16 million American adults have some form of depression.13

Anxiety Disorders

Anxiety is the body's response to a real or perceived threat. It causes feelings of excessive worry and fear. Anxiety disorders affect 40 million American adults.14

Eating Disorders

People with eating disorders may either overeat or starve themselves. Some people may have both of these disorders. About 30 million people in the U.S. will have eating disorders during their lifetimes.15

Attention Deficit Hyperactivity Disorder (ADHD)

ADHD commonly affects children aged 3 to 6 years. Some of them may continue to have the symptoms through their adulthood. ADHD causes hyperactivity, impulsivity, and problems with attention. About 6.1 million children in the U.S. have ADHD.16

Post-Traumatic Stress Disorder (PTSD)

Some people who have experienced or seen a traumatic event may have PTSD. PTSD causes flashbacks of the event, nightmares, and severe distress. Estimates suggest that 8 million Americans aged 18 years and older have PTSD.17


Schizophrenia is a severe mental disorder that causes hallucinations (seeing or hearing things that do not exist) and delusions. Schizophrenia affects about 3.5 million Americans.18

Drug and Alcohol Addiction

Addiction is a long-term mental disorder. People with addiction continue using alcohol or drugs despite the known harms. Addiction increases the risk of fatal overdoses. According to the CDC, drug overdoses caused 70,237 deaths in 2017.19


Autism usually begins in the first year of life. It causes problems with how a child communicates and socializes. Symptoms can include delayed speech, poor eye contact, and difficulty following directions. 1 in 59 children aged 8 years had autism in 2014.20


Learning Disabilities

A child with a learning disability has problems speaking, reading, and writing. Likewise, some may not be able to follow directions. Learning disabilities are not associated with intelligence.

Some common learning disabilities are:

  • Dyspraxia (speech difficulties)
  • Dysgraphia (bad handwriting)
  • Dyscalculia (problems with doing math)

In the U.S., learning disabilities affect 8% of children younger than 18 years.21

Personality Disorders

These disorders affect how a person thinks, behaves, and interacts in society. A person with a paranoid personality disorder has a distrust of people around them. About 9.2 million people in the U.S. have a paranoid personality disorder.22

How Psychologists and Medical Teams Work Together

The roles of psychologists depend on the settings they work in. For example, in primary care, they can help physicians detect depression and anxiety.

As a member of a medical team, a psychologist has the following roles:

Psychologists are experts in human behavior. They understand how thoughts affect behaviors. They work with other health professionals to prevent disease and promote healthy lifestyles.

Psychologists understand that physical health and mental health are interrelated. They can teach the skills necessary for preventing/managing physical and mental health problems.

They can help identify and treat mental illnesses in specific populations. For example, they help diagnose ADHD in children and dementia in older adults.

Psychologists can assess the healthcare needs of a community. If many people in a community are addicted to a drug, they can help design programs that target those people. Well-designed treatment programs help reduce the cost of treatment and optimize outcomes.

Psychologists can train and supervise family members of an affected person. Psychological consultation can help other health professionals understand the illness better.

How Does a Psychologist Conduct Psychological Diagnostic Testing?

The usual steps in psychological diagnostic testing are as follows:

After about a week, the patient (or a family member) will visit the psychologist to get a diagnosis. They may also inquire about the results of the test and recommendations.

First, the psychologist will take an hourlong interview. They will ask questions about the patient's concerns and family history. Moreover, they will help the patient understand the importance of the test. With the patient's consent, they will check records from the patient's physician, neurologist, and teachers.

On the next day, the patient will take the test. This may take one to five hours, depending on the type of test. Breaks will be provided, such as a lunch break or bathroom breaks. The test may have more than one session.

The psychologist will tell the diagnosis and explain what it means. They will also recommend therapies. If the patient is not happy with the diagnosis, they may ask for a second or another test.

Hearing the diagnosis can be challenging, especially if the report shows serious disorders like schizophrenia. Thus, the patient should take a friend or family member with them.

What are the Risks Associated with Psychological Diagnostic Testing?

Psychological diagnostic testing has no significant risk. That said, some tests may not be accurate or may have validity issues. Socio-cultural or language barriers may affect the test results.

Why Psychologists are Important to Recovery

For people with mental health diagnoses, the road to recovery can take many years. Recovery has two main components: diagnosis and treatment.


Proper diagnosis is the first step in recovery. Sadly, many cases of mental health issues go undiagnosed. Even worse, misdiagnosis is increasingly common. For example:

Up to 70% of depressed people do not receive the diagnosis of depression in primary care.23

4 in 10 people who die by suicide have visited their primary care physician within 30 days before their suicide.23

69% of people with bipolar disorder are misdiagnosed in the initial stages.24

33% of people with bipolar disorder remain misdiagnosed for over a decade.24



A psychologist can not only help with diagnosis but also treat a mental disorder. They can differentiate between psychological and physical causes of mental illness. With their knowledge of human behavior, an effective treatment plan can be developed. Notably, psychological interventions can help people stick to their treatment plans. Medications combined with psychotherapy often give the best results. Wellness is within reach.