Hi, Thanks for writing in. Cancer is a chronic condition and treatment takes months to years. It i s possible that a patient who is under treatment might have subjective problems like difficulty to concentrate, maintain a level of mental awareness and also unable to comfort oneself at any point during treatment. This might manifest as mild depression and a low mood state. Depression is defined as persistent low mood and inability to appreciate the joys of living under normal circumstances for more than 21 days continuously. If you are have slight mood variations then that is not depression but an adjustment to your variable life events taking place due to your illness. If there is persistent low mood then it can be classified as depression and you can talk to a psychologist to make you feel comfortable. From the medications mentioned, steroids can cause depression but this is subjective and not the same in every person taking it. Medications commonly prescribed for cancer patients can be one of those risk factors. Please do not worry.