Lethargy is the experience of feeling fatigue, which comes along with depression. It causes a significant decrease in energy that affects your performance in most tasks. Lethargy is both physical and mental when you are depressed. You feel tired or physically "run-down" all the time. Mental lethargy is experienced as a sense of on-going drowsiness. The drowsiness which comes with mental lethargy is different than the feeling of sleepiness that comes right before falling asleep.
Symptoms of Decreased Alertness
A decrease in mental alertness shows during your waking hours. A decrease in your usual startle response is one of the most noticeable. A loud noise or surprising event will not startle you. In general, lethargy causes your mental and physical responses to be delayed or muted. You may also experience a severe decrease in physical energy. Your energy levels can be so low that even the most simple task, such as taking care of your basic hygiene, can become difficult.
Symptoms of Cognitive Impairment
Lethargy creates a slowing of your cognitive functions, creating impairments in your memory and concentration. It becomes difficult for you to retrieve learn information. Your thinking becomes slower and mental task which were once simple become extremely difficult or impossible to perform. These impairments result in decreased problem-solving and decision-making skills.
Symptoms of Sleep Disturbance
Feelings of lethargy are thought to come from the reticular activating system (RAS) in the lower brain. The RAS is the area of the brain that regulates arousal, including the process of falling asleep and waking up. For this reason, you experience various symptoms of disturbed sleep. These include difficulty falling asleep (even though you feel tired most of the day), difficulty waking up and difficulty staying asleep through the night.
Although the primary emotion associated with depression is sadness, lethargy creates other emotional symptoms. The multitude of impairments you experience from lethargy makes your daily tasks challenging. As tasks you once found easy become increasingly difficult, you may experience emotions such as frustration and irritability. You may also experience hopelessness because of this cycle of impairment, along with poor decision making and feelings of frustration. This cycle is difficult for you to break on your own.