A method for treating or preventing depression is disclosed. The method, in preferred embodiments includes therapy apparatus for treating a patient's brain is provided. The method, in a preferred embodiment, includes irradiating at least a portion of a patient's brain with light energy having an efficacious power density and wavelength. The light energy should be sufficient to cause regulation of neurotransmitters in the brain and/or an upregulation of endogenous compounds in the brain, including neurotrophic factors, that result in neural growth, neurogenesis, and/or plasticity of neural function which leads to a diminishment or elimination of depression and its symptoms, and/or delays, reduces, or eliminates the onset of depression or depressive symptoms.