The question asked by you has been researched by several psychiatrists because a there were and still are several patients of depression who present to the out patient department with complaints of memory loss.Now even though depression as such has not proven to cause memory loss, it could be associated with it.
Memory loss (amnesia) is unusual forgetfulness. One may not be able to remember new events, recall one or more memories of the past, or both. Memory loss may be for a short time and then resolve (transient) or it may not go away and depending on the cause, get worse with time. Now it is important to understand that normal aging can cause some forgetfulness, it is normal to have some trouble learning new material or needing more time to remember it. But normal aging does not lead to dramatic memory loss which may be seen to be associated with depression.
Memory loss and an inability to focus may not seem like obvious symptoms of depression but they are often connected. Many areas of the brain are involved with the creation and retrieval of memories and irregularities in these areas, including those that create depression symptoms can affect how you process memories and also influence your ability to concentrate.
Research has suggested that processing speed that is the ability to take in information quickly and efficiently is impaired in individuals who are depressed.
Stress and anxiety that you may face if you are depressed can also get in the way of concentration. When you are tense and your mind is overstimulated or distracted, your ability to remember can suffer. Stress caused by an emotional trauma can also lead to memory loss.
Impairments in concentration and sustained attention in victims of depression are likely to influence memory deficits
--> Forget a specific word he or she wants to use (aphasia)
--> Forget the content of a conversation from the previous day
--> Forget what happened in a book recently read
--> Have trouble with "working memory" and not be able to remember specifics about their own autobiographical history.
Typically, routines are not forgotten nor are skills but verbal memory may be particularly affected by depression. Memory impairments are seen across age groups but tend to be worse in the elderly.
It's also important to realize that some medications used to treat depression may also have memory impairment as a side effect. Depressed individuals often succumb to alcoholism, smoking, substance abuse and altered sleep habits all of which have been recognised causes of memory loss.
--> Smoking harms memory by reducing the amount of oxygen that gets to the brain. Studies have shown that people who smoke find it more difficult to put faces with names than do nonsmokers.
--> Illicit drugs can change chemicals in the brain that can make it hard to recall memories.Sleep deprivation, both quantity and quality of sleep are important to memory. Getting too little sleep or waking frequently in the night can lead to fatigue,which interferes with the ability to consolidate and retrieve information.Good nutrition including high-quality proteins and fats is important to proper brain function. Depressed individuals have decreased appetite and deficiencies in vitamin B1 and B12 specifically can affect memory.
Hence yes, depression can cause memory loss and if you are facing any such problems, you must consult a psychiatrist.