A psychologist studies normal and abnormal mental states, perceptual, cognitive, emotional, and social processes and behavior by experimenting with, and observing, interpreting, and recording how individuals relate to one another and to their environments.^[2]

Psychologists can be seen as practicing within two general categories of psychology: applied psychology which includes "practitioners" or "professionals", and research-orientated psychology which includes "scientists", or "scholars". The training models endorsed by the American Psychological Association (APA) require that applied psychologists be trained as both researchers and practitioners,^[3] and that they possess advanced degrees.

Psychologists typically have one of two degrees: PsyD or PhD. The PsyD program prepares the student only for clinical practice (e.g., testing, psychotherapy). Depending on the specialty (industrial/organizational, social, clinical, school, etc.), a PhD may be trained in clinical practice as well as in scientific methodology, to prepare for a career in academia or research. Both the PsyD and PhD programs prepare students to take state licensing exams.

Within the two main categories are many further types of psychologists as reflected by the 56 professional classifications recognized by the APA,^[4] including clinical, counseling, and educational psychologists. Such professionals work with persons in a variety of therapeutic contexts. People often think of the discipline as involving only such clinical or counseling psychologists. While counseling and psychotherapy are common activities for psychologists, these applied fields are just two branches in the larger domain of psychology.^[5] There are other classifications such as industrial, organizational and community psychologists, whose professionals mainly apply psychological research, theories, and techniques to "real-world" problems of business, industry, social benefit organizations, government,^[6][7][8] and academia.

Clinical and counseling psychologists can offer a range of professional services, including:^[9]

In practice, clinical and counseling psychologists might work with individuals, couples, families, or groups in a variety of settings, including private practices, hospitals, mental health organizations, schools, businesses, and non-profit agencies.

Most clinical and counseling who engage in research and teaching do so within a college or university setting. Clinical and counseling psychologists may also choose to specialize in a particular field. Common areas of specialization, some of which can earn board certification, include:^[10]

Clinical and counseling psychologists receive training in a number of psychological therapies, including behavioral, cognitive, humanistic, existential, psychodynamic, and systemic approaches, as well as in-depth training in psychological testing, and to some extent, neuropsychological testing.

Although clinical and counseling psychologists and psychiatrists share the same fundamental aim—the alleviation of mental distress—their training, outlook, and methodologies are often different. Perhaps the most significant difference is that psychiatrists are licensed physicians, and, as such, psychiatrists are apt to use the medical model to assess mental health problems and to also employ psychotropic medications as a method of addressing mental health problems.^[11]

Psychologists generally do not prescribe medication, although in some jurisdictions they do have prescription privileges. In five US states (New Mexico, Louisiana, Illinois, Iowa, and Idaho), psychologists with post-doctoral clinical psychopharmacology training have been granted prescriptive authority for mental health disorders.^[12][13]

Clinical and counseling psychologists receive extensive training in psychological test administration, scoring, interpretation, and reporting, while psychiatrists are not trained in psychological testing. In addition, psychologists (particularly those from Ph.D. programs) spend several years in graduate school being trained to conduct behavioral research; their training includes research design and advanced statistical analysis. While this training is available for physicians via dual MD/Ph.D. programs, it is not typically included in standard medical education, although psychiatrists may develop research skills during their residency or a psychiatry fellowship (post-residency). Psychologists from Psy.D. programs tend to have more training and experience in clinical practice (e.g. psychotherapy, testing) than those from Ph.D. programs.

Psychiatrists, as licensed physicians, have been trained more intensively in other areas, such as internal medicine and neurology, and may bring this knowledge to bear in identifying and treating medical or neurological conditions that present with primarily psychological symptoms such as depression, anxiety, or paranoia, e.g., hypothyroidism presenting with depressive symptoms, or pulmonary embolism with significant apprehension and anxiety.^[14]

To become a psychologist, a person often completes a degree in psychology, but in other jurisdictions the course of study may be different and the activities performed may be similar to those of other professionals.^[15]

In Australia, the psychology profession, and the use of the title "psychologist", is regulated by an Act of Parliament, the Health Practitioner Regulation (Administrative Arrangements) National Law Act 2008, following an agreement between state and territorial governments. Under this national law, registration of psychologists is administered by the Psychology Board of Australia (PsyBA).^[16] Before July 2010, the professional registration of psychologists was governed by various state and territorial Psychology Registration Boards.^[17] The Australian Psychology Accreditation Council (APAC) oversees education standards for the profession.

The minimum requirements for general registration in psychology, including the right to use the title "psychologist", are an APAC approved four-year degree in psychology followed by either a two-year master's program or two years of practice supervised by a registered psychologist.^[18][19] However, AHPRA (Australian Health Practitioner Regulation Agency) is currently in the process of phasing out the 4 + 2 internship pathway. Once the 4 + 2 pathway is phased out, a masters degree or PhD will be required to become a psychologist in Australia. This is because of concerns about public safety, and to reduce the burden of training on employers. There is also a '5 + 1' registration pathway, including a four-year APAC approved degree followed by one year of postgraduate study and one year of supervised practice.^[20][21] Endorsement within a specific area of practice (e.g. clinical neuropsychology, clinical, community, counselling, educational and developmental, forensic, health, organisational or sport and exercise) requires additional qualifications.^[22] These notations are not "specialist" titles (Western Australian psychologists could use "specialist" in their titles during a three-year transitional period from 17 October 2010 to 17 October 2013).^[23][24][25]

Membership with Australian Psychological Society (APS) differs from registration as a psychologist. The standard route to full membership (MAPS) of the APS usually requires four years of APAC-accredited undergraduate study, plus a master's or doctorate in psychology from an accredited institution. An alternate route is available for academics and practitioners who have gained appropriate experience and made a substantial contribution to the field of psychology.

Restrictions apply to all individuals using the title "psychologist" in all states and territories of Australia. However, the terms "psychotherapist", "social worker", and "counselor" are currently self-regulated, with several organizations campaigning for government regulation.^[26]

Since 1933, the title "psychologist" has been protected by law in Belgium. It can only be used by people who are on the National Government Commission list. The minimum requirement is the completion of five years of university training in psychology (master's degree or equivalent). The title of "psychotherapist" is not legally protected. As of 2016, Belgian law recognizes the clinical psychologist as an autonomous health profession. It reserves the practice of psychotherapy to medical doctors, clinical psychologists and clinical orthopedagogists.^[27]

In Finland, the title "psychologist" is protected by law. The restriction for psychologists (licensed professionals) is governed by National Supervisory Authority for Welfare and Health (Finland) (Valvira).^[28] It takes 330 ECTS-credits (about six years) to complete the university studies (master's degree). There are about 6,200 licensed psychologists in Finland.^[29]

In Germany, the use of the title Diplom-Psychologe (Dipl.-Psych.) is restricted by law, and a practitioner is legally required to hold the corresponding academic title, which is comparable to a higher M.Sc. degree and requires at least five years of training at a university. Originally, a diploma degree in psychology awarded in Germany included the subject of clinical psychology. With the Bologna-reform, this degree was replaced by a master's degree. The academic degree of Diplom-Psychologe or M.Sc. (Psychologie) does not include a psychotherapeutic qualification, which requires three to five years of additional training. The psychotherapeutic training combines in-depth theoretical knowledge with supervised patient care and self-reflection units. After having completed the training requirements, psychologists take a state-run exam, which, upon successful completion (Approbation), confers the official title of "psychological psychotherapist" (Psychologischer Psychotherapeut).^[30] After many years of inter-professional political controversy, non-physician psychotherapy was given an adequate legal foundation through the creation of two new academic healthcare professions.^[31]

Since 1979, the title "psychologist" has been protected by law in Greece. It can only be used by people who hold a relevant license or certificate, which is issued by the Greek authorities, to practice as a psychologist. The minimum requirement is the completion of university training in psychology at a Greek university, or at a university recognized by the Greek authorities.^[32] Psychologists in Greece are legally required to abide by the Code of Conduct of Psychologists (2019).^[33] Psychologists in Greece are not required to register with any psychology body in the country in order to legally practice the profession.

In the Netherlands, the title of "psychologist"^[34] is not restricted by law. The Dutch professional association of psychologists (NIP), using trademark law, posited its own title "Psychologist NIP" (Psycholoog NIP). This title is granted exclusively to holders of a master's degree in psychology after a year of postgraduate experience. The titles "psychotherapist" (psychotherapeut) and "healthcare psychologist" (gz-psycholoog for gezondheidszorgpsycholoog) are restricted through the Individual Healthcare Professions Act (wet BIG) to those who have followed further postgraduate (PsyD/DPsych or licentiate level) training. The use of the titles "clinical psychologist" (klinisch psycholoog) and "clinical neuropsychologist" (klinisch neuropsycholoog) are reserved for those who have followed specialist post-licentiate training.

In New Zealand, the use of the title "psychologist" is restricted by law. Prior to 2004, only the title "registered psychologist" was restricted to people qualified and registered as such. However, with the proclamation of the Health Practitioners Competence Assurance Act, in 2003, the use of the title "psychologist" was limited to practitioners registered with the New Zealand Psychologists Board. The titles "clinical psychologist", "counseling psychologist", "educational psychologist", "intern psychologist", and "trainee psychologist" are similarly protected.^[35] This is to protect the public by providing assurance that the title-holder is registered and therefore qualified and competent to practice, and can be held accountable. The legislation does not include an exemption clause for any class of practitioner (e.g., academics, or government employees).

In South Africa,^[36] psychologists are qualified in either clinical, counseling, educational, organizational, or research psychology. To become qualified, one must complete a recognized master's degree in Psychology, an appropriate practicum at a recognized training institution,^[37] and take an examination set by the Professional Board for Psychology.^[38] Registration with the Health Professions Council of South Africa (HPCSA)^[39] is required and includes a Continuing Professional Development component. The practicum usually involves a full year internship, and in some specializations, the HPCSA requires completion of an additional year of community service. The master's program consists of a seminar, coursework-based theoretical and practical training, a dissertation of limited scope, and is (in most cases) two years in duration. Prior to enrolling in the master's program, the student studies psychology for three years as an undergraduate (B.A. or B.Sc., and, for organizational psychology, also B.Com.), followed by an additional postgraduate honours degree in psychology; see List of universities in South Africa. Qualification thus requires at least five years of study and at least one internship. The undergraduate B.Psyc. is a four-year program integrating theory and practical training, and—with the required examination set by the Professional Board for Psychology—is sufficient for practice as a psychometrist or counselor.^[40]

In Sweden, the title "psychologist" is restricted by law. It can only be used after receiving a license from the government. The basic requirements are a completed five-year specialized course in psychology (the equivalent of a master's degree) and twelve months of practice under supervision. All other uses are banned, though often challenged.

The title "Psychotherapist" is governed by similar rules, but the basic educational demands require another one-and-a-half years (spread out over three years) in a specialized course in psychotherapy (courses vary regarding theory), in addition to an academic-level degree within a field concerning the treatment of people (psychologist, social worker, psychiatrist).

In the UK, "registered psychologist" and "practitioner psychologist" are protected titles.^[41] The title of "neuropsychologist" is not protected.^[41] In addition, the following specialist titles are also protected by law: "clinical psychologist", "counselling psychologist", "educational psychologist", "forensic psychologist", "health psychologist", "occupational psychologist" and "sport and exercise psychologist".^[42] The Health and Care Professions Council (HCPC) is the statutory regulator for practitioner psychologists in the UK. In the UK, the use of the title "chartered psychologist" is also protected by statutory regulation, but that title simply means that the psychologist is a chartered member of the British Psychological Society, but is not necessarily registered with the HCPC. However, it is an offense for someone who is not in the appropriate section of the HCPC register to provide psychological services.^[43] The requirement to register as a clinical, counseling, or educational psychologist is a professional doctorate (and in the case of the latter two the British Psychological Society's Professional Qualification, which meets the standards of a professional doctorate).^[44] The title of "psychologist", by itself, is not protected.^[41] The British Psychological Society is working with the HCPC to ensure that the title of "neuropsychologist" is regulated as a specialist title for practitioner psychologists.

In the UK, clinical psychologists undertake a doctorate in Clinical Psychology (D.Clin.Psych., Clin.Psy.D., or similar), which has both clinical and research components. This is a three-year full-time salaried program provided by thirty centers across the UK, sponsored by the National Health Service (NHS). These clinical-psychology doctoral degrees are accredited by the British Psychological Society and the HCPC. Entry into these programs is highly competitive and requires at least a three-year undergraduate degree in psychology, plus some form of experience, usually in either the NHS, as an assistant psychologist, or in academia, as a Research Assistant.^[45][46] More information about the path to training in the UK can be found at the central clearing house for clinical psychology training applications ^[79] , and at www.ClinPsy.org.uk ^[80] , where questions can be answered on the forum run by qualified UK clinical psychologists.

As of December 2012, in the United Kingdom, there are 19,000 practitioner psychologists registered^[47] across seven categories: clinical psychologist, counseling psychologist, educational psychologist, forensic psychologist, health psychologist, occupational psychologist, sport and exercise psychologist. At least 9,500 of these are clinical psychologists,^[48] which is the largest group of psychologists in clinical settings such as the NHS. Around 2,000 are educational psychologists.^[49]

A professional in the U.S. or Canada must hold a graduate degree in psychology (MA, Psy.D., Ed.D., or Ph.D.), or have a state license to use the title psychologist.^[50][51] The exception to this is the profession of school psychology, which most states certify or license separately or under different requirements than healthcare provider psychologists. The most commonly recognized psychology professionals are clinical and counseling psychologists, who provide psychotherapy, or administer and interpret psychological tests. Requirements vary state-by-state for academics in psychology, as well as for government employees.

Psychologists in the United States campaigned for legislative changes to enable specially trained psychologists to prescribe psychiatric medicine. Legislation in Idaho, Iowa, Louisiana, New Mexico, and Illinois has granted those who complete an additional master's degree program in psychopharmacology permission to prescribe medications for mental and emotional disorders.^[52] As of 2019, Louisiana is the only state where the licensing and regulation of the practice of psychology by medical psychologists (MPs) is regulated by a medical board (the Louisiana State Board of Medical Examiners) rather than a board of psychologists.^[53] While other states have pursued prescriptive privileges, they have not succeeded. Similar legislation in the states of Hawaii and Oregon passed through their respective legislative bodies, but in each case the legislation was vetoed by the state's governor.^[52]

In 1989, the U.S Department of Defense was directed to create the Psychopharmacology Demonstration Project (PDP). By 1997, ten psychologists were trained in psychopharmacology and granted the ability to prescribe psychiatric medications.^[54]

In the United States and Canada, full membership in the American Psychological Association requires doctoral training (except in some Canadian provinces, such as Alberta, where a master's degree is sufficient).^[1] The minimal requirement for full membership can be waived in circumstances where there is evidence that significant contribution or performance in the field of psychology has been made. Associate membership requires at least two years of postgraduate studies in psychology or an approved related discipline.^[55]

There are a number of U.S. schools offering accredited programs in clinical psychology resulting in a master's degree. Such programs can range from forty-eight to eighty-four units, most often taking two to three years to complete after the undergraduate degree. Training usually emphasizes theory and treatment over research, quite often with a focus on school, or couples and family counseling. Similar to doctoral programs, master's level students usually must fulfill time in a clinical practicum under supervision; some programs also require a minimum amount of personal psychotherapy.^[56] While many graduates from master's level training go on to doctoral psychology programs, a large number also go directly into practice—often as a licensed professional counselor (LPC), marriage and family therapist (MFT), or other similar licensed practice.

There is stiff competition to gain acceptance into clinical and counseling psychology doctoral programs (acceptance rates of 2-5% are not uncommon). Clinical and Counseling psychologists in the U.S. undergo many years of graduate training—usually five to seven years after the bachelor's degree—to gain demonstrable competence and experience. Licensure as a psychologist takes an additional one to two years post Ph.D./Psy.D. (licensure requires 3,000 hours of supervised training), depending on the state. Today in America, about half of all clinical and counseling psychology graduate students are being trained in Ph.D. programs that emphasize research and are conducted by universities—with the other half in Psy.D. programs, which have more focus on practice (similar to professional degrees for medicine and law).^[57] Both types of doctoral programs (Ph.D. and Psy.D.) envision practicing clinical and counseling psychology in a research-based, scientifically valid manner, and most are accredited by the American Psychological Association.^[58]

APA accreditation^[59] is very important for U.S. clinical, counseling, and school psychology programs because graduating from a non-accredited doctoral program may adversely affect employment prospects and present a hurdle for becoming licensed in some jurisdictions.^{[60][61][62][63]}

Doctorate (Ph.D. and Psy.D.) programs usually involve some variation on the following 5 to 7 year, 90-120 unit curriculum:

The practice of clinical and counseling psychology requires a license in the United States and Canada. Although each of the U.S. states is different in terms of requirements and licenses (see^[64] and^[65] for examples), there are three common requirements:^[66]

All U.S. state, and Canada provincial, licensing boards are members of the Association of State and Provincial Psychology Boards (ASPPB) which created and maintains the Examination for Professional Practice in Psychology (EPPP). Many states require other examinations in addition to the EPPP, such as a jurisprudence (i.e. mental health law) examination or an oral examination.^[66] Most states also require a certain number of continuing education credits per year in order to renew a license. Licensees can obtain this through various means, such as taking audited classes and attending approved workshops.

There are professions whose scope of practice overlaps with the practice of psychology (particularly with respect to providing psychotherapy) and for which a license is required.

In the United States, of 170,200 jobs for psychologists, 152,000 are employed in clinical, counseling, and school positions; 2,300 are employed in industrial-organizational positions, and 15,900 are in "all other" positions.

The median salary in the U.S., in 2012, for clinical, counseling, and school psychologists was US$69,280 and the median salary for organizational psychologists was US$83,580.^[2][78]