Dementia
Dementia is a disorder associated with cognitive ability and it is more commonly found in older population but this does not mean that it cannot happen to young adults. Apart from memory, dementia can affect other cognitive abilities, like, attention, problem solving ability and language. The personality of the sufferer may change significantly and he or she may not be able to carry out even simple day-to-day activities at the later stages of dementia. However, some cases of dementia are reversible with proper treatment.

Drug and Alcohol Abuse
Excessive consumption of alcohol and drug addiction can adversely affect both mental and physical well-being of individuals. Drug and alcohol abuse are often major contributory factors for a number of problems related to mental health. They can impair normal functioning of the nervous system, which in the long run may result in memory loss. In the short run, drug and alcohol abuse causes a state of intoxication which is associated with temporary loss of memory.

Brain Tumors
Brain tumors can impair the functioning of a particular part of the brain where they develop. So, if a tumor develops in the part of the brain which is associated with memory, then it can affect memory to a great extent. Tumors can be both benign and malignant. The benign tumors remain confined to the particular area of origination and do not pervade other places, while the malignant ones can spread rapidly, pervading the surrounding healthy tissues.

Alzheimer's Disease
Alzheimer's disease is one of the most common types of dementia or degenerative diseases. The most common symptom of this condition is loss of memory and cognitive abilities. Initially, the sufferer develops forgetfulness about recent events but their long-term memory remain intact. However, gradually over a period of time, the disease also affects their long-term memory.

Stress
Stress is a state of mental or emotional strain or fatigue. This indicates that the brain or human mind is subject to a lot of work, more than it can handle. So, stress basically involves overworking of the brain, which results in mental fatigue. In order to overcome this situation, the brain needs to rest and slow down. Stress affects memory and learning ability of an individual. This is the reason why we fail to recall or learn new things when we are mentally stressed. To prevent stress related loss of memory and learning ability, one has to address the factors that increase stress and anxiety and deal with them.

Depression and Anxiety
Like stress, depression and anxiety too have a negative impact on memory. They not only impair memory but can also affect physical and mental well-being of an individual.

Head Injury
As our brain is the main site for storing, processing and recalling information, any physical injury to this part can cause mild to major loss of memory. The extent to which head injury can affect memory depends on the severity of damage to the brain. Severe injury to the head can even result in permanent loss of memory.