It gets believed that the practice came to be towards the start of the twentieth century in 1896. Lightner Witmer opened up a center at the University of Pennsylvania where he sought to study mental issues and help people out of their distress. For the first few decades in the twentieth century, the practice mainly focused on the assessing of the problems but did not delve much into looking for solutions to the issues.
However, this came to change after the Second World War. Many people suffered trauma during the war, and there was a need for clinicians to come in and find ways to help people deal with the distress positively. As such, many people underwent training in this profession and became certified clinicians who people could consult when they felt overwhelmed.
The increasing number of people who needed counseling led to the development of three branches of the practice. There is the clinical science branch which focuses on finding the causes of mental issues so that psychology can be more efficient. Their study helps other clinicians in the sector in finding solutions.
The second branch is the science-practitioner model. As the name suggests, it involves studying issues, and after finding solutions to the problems, it puts them into practice by treating patients using the discovered formulas. The last branch is the practitioner-scholar model which has its focus on clinical practice. What they do is they hold sessions with their clients, assess the issues at hand and help them through the process of healing.