Reducing Complex Psychological Processes to Biology?

I think currently at this time it is not possible to explain psychology only on the fundamental basis of biology alone. Reductionism is examining human behavior and psychology by examining how smaller systems work throughout the human body. The theory suggests that behavior and mental processes can be explained by basic sciences such as biology. Although we can examine how the brain responds, it does not explain why certain behavior takes place. For example, an individual running away from a dog would be possible due to a stress response, which allowed the individual to run fast, but this does not explain why the individual was scared in the first place. Perhaps an event took place within their childhood or early youth that instilled a lifelong fear of dogs, perhaps they don’t know why they ran from the dog in the first place. Biology cannot simply explain why the individual behaved the way they did. Furthermore, if we look at mental disorders, in particular, many individuals suggest that mental disorders are primarily caused due to chemical imbalances in the brain. However we are ignoring social factors that also influence mental and health disorders. In my personal opinion, I think psychology and the human mind would be understood better if we examine all aspects such as social factors and biological factors. I do not believe that psychology as of yet can be reduced to just biology as they are many questions in regards to human behavior that remain unanswered.