I am male 21 years old. i tend to forget often of what i was thinking or where i leave my belongings. are their reasons behind this problem?

Not unusual: Seriously doubt you have dementia. All of us get forgetful, at times, and the stress of daily life can be distracting. Anxiety and depression, lack of sleep, and various medications can all make this worse. Some pts with migraines get periodic cognitive issues, and epileptic partial seizures can do this also. Best place to start: evaluate emotions and sleep.

Many reasons: One common cause for "forgetfulness" in a young adults is drug use. Another is unrecognized adhd. Depression, anxiety disorder and many other conditions including anemia, iron deficiency, sleep deprivation or apnea can also cause this. Please see your doctor for a full work up, particularly if this is of recent onset.

COMPLICATED: These are a collection of issues or symptoms that could be indicative of add. However, the diagnosis can only be made if there have been problems with focus and concentration since childhood even if it was not diagnosed at thst time. Would also need to know other things like medications you take. Any alcohol or drug usage. Sleep patterns or a history of head injury. Speak to your physician.