The average mean indicates that antidepressants can usually help make a person's life better.
However, antidepressants alone are not a treatment for depression, though they are often an important part of that treatment. Depression has a physical cause, but there is more to it than just balancing the chemicals in the brain. The entire body is involved, including the hormones, central and peripheral nervous systems, musculature, skin, and all our senses. The impact our experiences have is also a factor. Cases of depression vary from mild clinical depression to major depressive disorder, and only a trained professional can help assess the severity of depression and suggest a course of action.
See:
What Causes Depression - Harvard Health