There seems to be a correlation between MDD and lack of motivation, however, one of the symptoms of MDD is lack of motivation. Thus, with other risk factors such as age, neurodegenerative diseases and others on a long term can contribute in depression.
Indeed a sudden appearance of lack of motivation to do what we used to do or to do the necessary works for life, is a swing of a mood change and if that continues for a measurable length of time, it brings a lose of appetite to the essence and very purpose of life and and living which is a precursor for depression. In such a case self awareness and to find reasons why such a behavioral change happens to rectify the problem and come out of that state of existence or immediate psychiatric attention is required.
Depression is a serious illness, and focusing on a goal, a hobby, or even a strong family unit to get you through it may not be enough. Treatment of depressive episodes frequently require medication and counseling from qualified mental health experts to help you rekindle the motivation you need to get back to a better quality of life.
Unfortunately, many people believe that people who are depressed lack motivation, and they assume that’s the cause of their depression. They also believe that the depressed person needs to just ‘snap out of it.’ In reality, motivation requires desire and positive, creative energy. Depressed people often lack those two key requirements. Trying to motivate a depressed person by encouraging them to go out, get active, and have fun often fails. indeed I agree a lack of motivation is one of the strongest indicators of depression.
My take is, not necessarily, if we take the everyday understanding of the words involved. I am thinking of the guy from a Russian movie of Nikita Mikhalkov....Oblomov... he was hardly motivated ... but I would not say he was a depressed person. It is true that ...this is just a movie, but it seems like it was a copy of reality of some 1800 Russia...
Think there are many factors influencing depression. Not sure lack of motivation can influence depression. Because according to Herzberg's Motivation-Hygiene Theory, satisfaction can due to motivation factor (e.g. achievement, recognition, advancement, growth etc) and hygiene factor (e.g. security, salary, work conditions, supervision etc). Not sure lack of motivation factor or hygiene factor or both factors can influence depression. Perhaps more research is required or if anyone had conducted such research can share their findings? Thanks.
Lack of motivation may make an individual lazy and inactive. This need not be a cause for the depression. On the other side, inability for doing some we really want to do may be a cause for depression.