What Is Lethargy? - Definition, Causes & Symptoms

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  • 0:00 Definition of Lethargy
  • 1:08 Causes of Lethargy
  • 3:01 When It Becomes Serious
  • 3:32 Lesson Summary
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Lesson Transcript
Instructor: Emily Smathers
In this lesson, we will uncover the mystery of lethargy. We will examine the definition, causes, and symptoms of lethargy. We will also learn of the different diseases that have lethargy as a symptom.

Definition of Lethargy

Have you ever woken up and felt like it would be better to stay in bed? Felt so tired that it would be too much effort to get up? At what point does this feeling go from general tiredness to common lethargy to a medical condition that needs professional assistance? In this lesson, we will learn some of these common differences.

Lethargy is defined as a state of sluggishness, inactivity, and apathy. Other words are also associated with lethargy, such as listless, tiredness, lack of energy, continued sleepiness, and others. All of us have had that feeling from time to time, and having a loss of energy naturally occurs after you're physically engaged. Lethargy can also occur after long periods of time - days or weeks - when the body is physically or intellectually spent. A common collegiate time of feeling lethargic is after finals. Students can spend days and perhaps weeks working hard to finish assignments from their professors, and at the end of the semester when they can take a break, they are exhausted mentally and physically. This would be considered lethargy.

Causes of Lethargy

Lethargy is typically a symptom of a disease, and it has varied levels of medical seriousness. Overworking for extended periods of time is a common cause of lethargy, but it is far from the only one. Other causes of lethargy could be divided into different types. These types would include physical and psychosocial; heart and vascular; and disease-related.

Physical and Psychosocial:

In our busy world, stress and overwork are a common source of lethargy. After working in a high pressure, high demand position, it is easy for stress to use the physical and mental reserves a person would have, making him or her listless and tired. Other times, lethargy can be caused by lack of exercise, alcohol use, or eating disorders. In these cases, the less you do, the more lethargic you can feel, and this can become a vicious cycle that is difficult to overcome. This could lead to disorders, such as depression or anxiety, which also have related lethargy. At this point, medical assistance should be sought.

Heart and Circulatory Diseases:

Heart and circulatory diseases can create lethargy as a result of diseases such as cardiomyopathy or stroke. These patients can have lethargy due to their inability to move well and tire easily due to their compromised physical ability. The heart does not pump blood well, resulting in less oxygen being distributed to the body, and the body cannot keep moving and must rest. This can decrease the patient's motivation and ability to exercise, leading to less exercise, greater lethargy and increased risk of greater disease.

Neurological Diseases:

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