What is Major Depressive Disorder (MDD)? (SL IB Psychology)

• Low mood which is persistent and ongoing
• The inability to take pleasure in life, even from experiences or activities that usually promote pleasure e.g. I used to love swimming every morning but now it fills me with no joy at all
• Intense, overwhelming feelings of sadness, self-blame, guilt, worthlessness, hopelessness
• The inability to take action or make decisions 
• An absence of motivation and/or sense of purpose, an increase in apathy
• Sleeping more than usual or, conversely, restlessness and insomnia
• Loss of appetite or, conversely, comfort eating

How does MDD impact the life of the depressed person?

• MDD can become a blight on someone’s life as it impacts their ability to conduct their life as they normally would, impacting everyday routines as well as pleasurable activities and experiences
• MDD can adversely affect relationships e.g. low mood may lead to the depressed person expressing anger towards others; the depressed person’s lack of interest in life means that they are unlikely to want to engage in activities with others
• MDD can lead to the depressed person wishing to withdraw from life which has obvious implications as to their working life as well as their relationships
• MDD has been identified as one of the leading factors in disability across the world (The National Library of Medicine, June 2022)
• MDD can be the trigger for comorbidity as it may be the gateway into other disorders e.g. substance abuse disorder, anxiety disorders
• MDD may exacerbate existing medical conditions such as heart disease, diabetes, hypertension
• MDD brings with it the risk that the depressed person will engage in self-harm which could escalate potentially to them being vulnerable to suicide

MDD can severely impact life.

• MDD is one of the most prevalent mental disorders, having a lifetime prevalence of 5-17% (National Library of Medicine, June 2022)
• MDD is often referred to as the ‘common cold of mental disorders’ (Psychology Today, November 2008) as it affects large numbers of people at any given time
• Women are more likely to report depressive symptoms than men
• Men may under-report or ignore depressive symptoms due to a range of factors e.g. not wishing to ‘make a fuss’, social conditioning which may suggest that depression is not ‘manly’, not having the language to be able to discuss feelings in the same way that women do
• An estimated 21.0 million adults in the USA had at least one major depressive episode  i.e. 8.3% of all U.S. adults in 2021 (The National Institute of Mental Health, July 2023)
• MDD affects all sectors of society: being wealthy or successful does not safeguard someone against developing MDD
• MDD may be expressed or reported in different ways according to culture

Which studies investigate MDD?

• Caspi et al. (2003) - a biological explanation of MDD

• Grazioli & Terry (2000) - a cognitive explanation of MDD

• Lewinsohn et al. (1990) - a sociocultural explanation of MDD

All three of these studies, Caspi et al. (2003), Grazioli & Terry (2000) and Lewinsohn et al. (1990) are available as Key Studies of Explanations of MDD – just navigate the Explanations for Disorders section to find them.