¶ … clinical psychology as a distinct pursuit and profession emerged in the late nineteenth century. However, a "climate of ideas receptive to the development of clinical psychology" emerged as early as the late 18th century (Reisman, 1976, p. vii). Clinical psychology perspectives reflected trends in Enlightenment thinking and the rise of the scientific method as a primary means of investigating reality. Enlightenment issues like individualism underlie much of clinical psychology. The evolution of the professional field indicates the important role of both scientific research and methodology including statistical analysis. Imbuing psychology with the scientific method allowed clinical psychology to emerge as a credible profession dedicated to the explication and healing of mental health issues. Clinical psychology is one of many approaches to psychology and mental health. Psychiatry, counseling psychology, and social work all share elements in common with clinical psychology even though all are distinct professions. Reisman (1976) defines clinical psych as "a branch of psychology devoted to the search for, and the application of, psychological principles and techniques that contribute to the understanding of individuals and that may be used to promote their more effective functioning," (p. 2). The history of psychology as an investigation of the human psyche far predates the emergence of clinical psychology. An early medical model of the human psyche was postulated by Hippocrates, for example, (Fazakas-DeHoog, n.d.). However, the first fusion of experimental science and psychology took place in the late nineteenth century. "Clinical psychology emerged as a profession in the United States in the 1890s," concurrent with academic inquiry in Europe and North America. As Fazakas-DeHoog (n.d.) points out, Wilhelm Wundt developed one of the first known psychology laboratories at the University of Leipzig. Wundt's laboratory was a significant breakthrough, revealing "a deep link between clinical and experimental psychology since clinical psychology has a very clear disposition to research," ("Brief Institutional History of Clinical and Health Psychology," n.d.). For example, observable phenomenon like perception and cognition were investigated in a clinical setting in Wundt's laboratory (Fazakas-DeHoog, n.d.). Wundt also initiated the first psychology research journal, coursework, and textbook (Fazakas-DoHoog, n.d.). In the United States, William James spearheaded the development of clinical psychology at Harvard University. James integrated principles of psychology and comparative religion into his theories of human psychology (Fazakas-DeHoog, n.d.).

The solidifying of clinical psychology into an academic discipline gave rise to the American Psychological Association (APA), the founding of which marks one of the most important events in the history of the profession. During the first several decades of the twentieth century, clinical psychology defined and codified its subject matter, creating "its own institutions (journals, associations) into the frame of the academic and scientific psychology, mainly represented by University and APA," ("Brief Institutional History of Clinical and Health Psychology," n.d.). Briefly, in 1919, clinical psychology even boasted its own separate professional organization called the American Association of Clinical Psychology. This was soon subsumed into the greater rubric of the American Psychological Association.

Before the Second World War, the emphasis in clinical psychology was on assessment: on recognizing patterns, discovering causes, and presenting coherent theories. Intelligence testing became fundamental to clinical psychology around the First World War. The American military embraced early assessments as possible means to make scientific predictions about soldiers but also about civilian populations (Gould 1982). Psychologist Robert Yerkes developed two intelligence tests specifically for the military: Army Alpha and Army Beta. Veterans' hospitals became primary workplace settings for clinical psychologists. The Army Beta test would later influence the development of Intelligence Quotient (IQ) tests (Gould, 1982). Personality testing using instruments like the Rorschach inkblots also became one of the hallmarks of clinical psychology prior to World War Two. In addition to assessments, "clinical psychologists developed research and theories on several topics, such as the nature of personality, the origin of intelligence…the causes of behavior disorders, the uses of hypnosis, and the link between learning principles and abnormal behavior," ("Brief Institutional History of Clinical and Health Psychology," n.d.).

The works of Sigmund Freud and Carl Jung garnered attention during the early and middle of the twentieth century. Clinical psychology occasionally, but not always, embraced psychoanalysis as a means to assess and treat patients. Issues such as licensure also become crucial to clinical psychology as the profession evolved from an academic to a practicing health care field.
Yet research and scholasticism remain central to clinical psychology; science in fact defines the profession and sets it apart from counseling psychology and psychoanalysis both. The Boulder Model was established to refers to the scientist-practitioner model that has characterized clinical psychology since the 1950s. Scientific research methodologies are applied to psychology by focusing on observable or measurable variables. Clinical psychologists use several methods of statistical analysis with research data: including analysis of variance (ANOVA), structural-equation modeling (SEM), and factor analyses. Theoretical models are used to guide research in clinical psychology, and comparison between those models is critical (Treat & Weesering, n.d.). The use of the scientific method gives rise to pertinent ethical issues that have been central to the evolution of clinical psychology. For example, informed consent was not always given to participants in research experiments but is now standard practice in the profession. In addition to ethical issues, issues related to validity and generalizability sometimes constrain the efficacy of clinical psychology research.

Professional degrees and licensure are also key components of the evolution of clinical psychology. Depending on local and state standards, licensure ensures that clinical psychologists are qualified to treat patients with mental health concerns. Standards of practice are governed by professional organizations like the APA as well as by academic institutions. As Richmond (2011) points out, in the United States, "tthe degrees associated with clinical psychology are the traditional Ph.D. (Doctor of Philosophy)…and the newer Psy.D. (Doctor of Psychology)." The PhD entails training in both research and treatment, whereas the PsyD more thoroughly emphasizes treatment and downplays research methods.

Thus, the PsyD is a degree that more closely resembles a degree in counseling psychology. Counseling psychology is narrower in scope than clinical psychology. A counseling psychologist rarely addresses serious mental health issues. The client's relationships and other life issues are discussed in a counseling session; a clinical psychologist uses various techniques to address issues that might stem from childhood such as trauma. Counseling psychology does not emphasize the importance of the past or the unconscious mind, but focuses almost exclusively on the present (Richmond, 2011). School psychologists and career counselors are often licensed counseling psychologists. In fact, counseling psychologists are not PhDs generally but frequently pursue an educational degree such as M.S. Or M.S.E. Or Ed.D. Clinical psychologists, on the other hand, frequently work in hospitals. A psychiatrist differs from a clinical psychologist in that psychiatrists are licensed physicians who specialize in mental health. Unlike clinical or counseling psychologists, psychiatrists are licensed to prescribe pharmacological interventions.

Conclusion

Clinical psychology is a distinct profession that focuses on applying scientific research to mental health problems. The profession is continually evolving, as new theories are applied to mental health. Clinical settings provide patient populations for treatment interventions, as well as patient populations used as research participants. Research and academia have been central to clinical psychology since its inception in the late nineteenth century, but so too has the application of that research to patients. Psychiatric and general health care institutions rely on clinical psychologists for the assessment and treatment of mental health issues. Clinical psychologists treat patients from a diverse demographic. Although counseling psychology, psychiatry, neuroscience, and other areas of psychological study have areas of intersection, clinical psychology has its own set of professional degrees and licensure programs.