One of my first exposures to studying psychology was my Introduction to Psychology class in my freshman year of college. Admittedly, I cannot describe many of the specifics of this class, but one general theme stayed with me throughout the rest of my formal training:

The cause of mental health problems can be found in biological, psychological, and social factors. 

My years of clinical practice have continued to strengthen this conviction and I continue to educate my clients on this concept.
Drawing a triangle with a circle around it, I begin my introduction:

Most people have a bias about where they believe mental health problems come from;
I assume you have one, and the people in your life have one. Some people believe these problems are biological … when this is the primary view, people often focus on medication as the treatment of choice. Some people believe these problems are psychological … often the focus is on telling the individual to stop thinking a certain way and start thinking a new way. Some people believe these problems are social … when this is the primary view people put priority on changing the externals in a person’s life – relationships, environment, or systems. Some people believe these problems are spiritual … when this is primary the individual is often encouraged towards certain religious beliefs, practices, or connection to God or a higher power.
My bias is that while these may hold different weight in the lives of people,
problems often stem from a combination of each of these four spheres for the individual.  

I have come to believe that clients are best served
when we together look at causes and solutions as multifaceted.
We may see positive change and increased health after addressing one or two spheres,
but we will likely see the most positive results when treatment addresses the person holistically,
recognizing the many dynamics at play and the ways these are interconnected.