It often happens that people believe they suffer from depression when in reality they simply feel sad. Sadness is caused by an event that is happening at a given time, as opposed to MDD (major depressive disorder), when the individual suffers from a constant feeling of conflicting emotions over a long period of time. Major depressive disorder is a mood disorder that makes you feel constantly sad and lonely. It also causes a loss of interest in past hobbies and activities and affects how you feel, think and behave. There are many symptoms and signs of major depressive disorder and they always have a cause, but there are always diagnoses and preventions for this terrible mood disorder. It is important to understand the symptoms and signs of someone who may be suffering from major depressive disorder. This will make it easier to distinguish who may need help or, more importantly, professional help. The most obvious sign for those suffering from major depressive disorder is the feeling of constant sadness and emptiness. This may also include guilt and worry about past failures or events. Those with major depressive disorder may also have difficulty sleeping and feel tired all the time, regardless of how much sleep they got the night before. It is also possible that the individual consistently oversleeps. There will most likely always be a loss of interest in past hobbies or everyday activities such as school. Suija, Kalda and Maaroos explained, after their 2009 study on how depression patients self-evaluate, that 24% of depressed patients said their social activities were affected by their health problems. Only 14% of non-depressed patients agreed.http://proxy4.vaniercollege.qc.ca:2234/ehost/pdfviewer/pdfviewer?sid=e461a...... half of the paper..... .s Collection . Network. May 1, 2014.Beck, Aaron T., M.D., and Brad A. Alford. Depression: causes and treatment. Np: University of Pennsylvania, 2009. Print. Canadian Government. Sante et services sociaux Quebec. Government of Quebec, 2014. Web. 01 May 2014. Mayo Foundation for Medical Education and Research. Depression (major depressive disorder). HONcode, 2014. Web. 1 May 2014. .Suija, Kadri, Ruth Kalda and Heidi-Ingrid Maaroos. “Patients with depressive disorder, their co-morbidities, visit rate, and disability in relation to self-assessment of physical and mental health: a cross-sectional study in family practice.” BMC Family Practice 10.(2009): 1-8. Academic research completed. Network. 01 May 2014.