Some men in their late 40s and early 50s develop depression, loss of libido, erectile dysfunction, and other physical and emotional symptoms such as irritability, loss of muscle mass and reduced ability to exercise, weight gain, lack of energy, difficulty sleeping, or poor concentration; many of these symptoms may arise from a midlife crisis or as the results of a long-term unhealthy lifestyle (smoking, excess drinking, overeating, lack of exercise) and may be best addressed by lifestyle changes, therapy, or antidepressants.