A growing body of evidence suggests that magnetic and electrostimulation of certain parts of the brain can alleviate depressive symptoms. Repetitive transcranial magnetic stimulation (TMS) as a treatment for depression has shown statistically significant effects, but the clinical significance of these effects has been questioned. Major depression is often difficult to diagnose accurately. Even when the diagnosis is properly made, standard treatment approaches (e.g., psychotherapy, medications, or their combination) are often inadequate to control symptoms or maintain initial benefit. There is a need for more effective and better-tolerated treatments. TMS is a noninvasive and easily tolerated method of altering cortical physiology. It is effective in treating depression with minimal reported side effects. The existing literature supports a possible role for TMS in the treatment of depression and suggests concurrent biomarkers, which may help in determining which group of patients would have a positive response to TMS treatment for major depressive disorder (MDD). Temperament and Character Inventory (TCI) appeared to be a cost-effective, promising predictor to TMS treatment response. The authors evaluated current potential difficulties in diagnosing MDD accurately and reviewed a personalized approach as a model that may help with diagnosing MDD more accurately as well as improving the existing TMS treatment.