Psychoanalysis is nothing to do with psycho therapy. His main theory was illness is caused by subconscious i.e. neurosis will abate if it can be discharged with no discomfort for the patient. If you accidentally catch your knuckles and take the top layer of skin off you do not feel pain until you see the damage. If you try and take a file and rub it on your knuckles then you find you cannot as you instantly feel the pain during the process. The whole is greater than the sum of the parts.
Many scientist expect that a theory only stands if it can be replicated over and over again.
So science can never truly replicate an experiment based on humans as their perceptions change each time they are involved in an experiment. People are not as predictable and so, not only external forces such as heat, light, smell, ergonomics and taste, can have an effect on an individual but also internal forces. How the person feels about themselves, do they have a headache, is there something bothering them, are they having a good day or bad day.