The feelings of empathy, kindness and consideration are simply byproducts of a chemical reaction?
Almost correct! More like the end result of a chemical reaction, rather than a "byproduct" (although some here may scream "semantics").
Furthermore, if these chemicals in the brain (known as "neurotransmitters") get out of balance, conditions such as depression usually result. Treatment for depression simply involves the correction of that chemical imbalance.