You may find user-friendly depression screening questionnaires online, such as the PHQ-9. These questionnaires can help you to learn the symptoms of depression, and to decide whether to seek out a mental health professional, or encourage someone to do so. However, questionnaires cannot take the place of a doctor or mental health professional who can help you to figure out why you are feeling the way you do. A trained professional can work with you to find out if you have a treatable illness or mental illness and get you started on the path to healing. You may wish to start by taking an online test, but the best way to get help is by meeting in person with your doctor or a mental health professional.