What is the impact of stress on the brain and memory processes

Memory difficulties are a broad concept and at the same time so universal that many people may have experienced them in their lives.

As the causes of such difficulties may be diverse, defining them is important in the process of diagnosis because, as it should be noted, memory difficulties are not always problems in the clinical sense. For example, the understanding of a cognitive process disorder is different in the course of chronic stress, metabolic changes in cancer, disorganisation of thinking in schizophrenia, after a stroke, in the course of dementia or after a sleepless night or substance abuse. Therefore, when the need arises, an accurate and professional diagnosis is important, especially since severe cognitive processing disturbances are never the only and isolated group of symptoms. In an in-depth interview it usually turns out that they are accompanied by other difficulties in the field of emotions, behaviour and social functioning, which may already create a constellation of symptoms in the form of a specific disorder. 

Memory is not a homogenous whole. To describe it, scientists apply various divisions, but this article will focus only on two of them: the division into long-term and short-term memory and the division into explicit and latent memory. Long-term memory applies to personal life events, facts, concepts and relations forming the basis of knowledge about the world as well as images - most often with a strong emotional content. No precise information in available on the capacity of long-term memory, but researchers tend to conclude that for biological reasons we are unable to use the entire capacity of our own memory anyway. Short-term memory is a storehouse that holds, for a very short period of time, a few pieces of information needed for the current activity (e.g. a telephone number you just want to call or a shopping list).

The division into explicit and latent memory refers to different forms of material storage and retrieval. Explicit memory applies to facts and events including the awareness of knowing them. Latent memory, together with its component of procedural memory, is the knowledge of how to do something, even without having to consciously think about the process. Information can be transferred between explicit and latent memory stores, e.g. when, after a period of conscious attempts to remember a material or activity, you suddenly realise that you can already do it. 

The situation is further complicated by the fact that brain structures responsible for emotions and memory are closely linked and interact with each other. An example of such a structure responsible for emotional reactions is the amygdala, which during severe stress activates large and highly active nerve fibres connecting it to the hippocampus. The activation of these pathways causes disturbances in the hippocampus. The amygdala can maintain a high level of activity in response to stress and not reduce it even after the threat has gone away. We may then feel anxious, fearful and see our memory deteriorate even when we are no longer under any real threat.

Stress, in particular chronic stress, affects the structures responsible for memory by:

1. the disruption of communication between the cells of the nervous system (neurons) or damage to their fragments,
2. the inhibition of the formation of new neurons,
3. the reduction of the glucose supply to the brain, which can lead to neuronal death.

The relationship between stress intensity and memory processes is described by the so-called inverted-U function. The most optimal state for our memory processes is the state of moderate arousal. The complete lack of stimulation or overstimulation causes memory deterioration. Research shows that the retrieval of previously remembered information is more sensitive to stress than the creation of new memories. In other words, you may learn something, but under stress it will be difficult for you to retrieve it from your memory.

You should pay special attention to the symptoms indicating the deterioration of cognitive processes in the following situations:

• (a) when you have observed significant general deterioration in your functioning in different areas of your life,
• b) when, despite the discontinuation of the stressful situation, your cognitive functions do not return to the state from before the crisis,
• c) after a head injury, poisoning (e.g. with drugs, psychoactive substances or other toxins) or the loss of consciousness,
• d) when cognitive decline is accompanied by other symptoms, e.g. decreased mood, anxiety, loss of interest in or satisfaction with activities important for you, sleep disorder, decreased libido, appetite disorder, the feeling of physical and mental fatigue, negative thinking about yourself, suicidal thoughts or any self-destructive behaviour, recurrent thoughts about some difficult event/threat or strange sensations (e.g. hallucinations).

In the above circumstances, it is recommended to consult a specialist who could - also using specialised diagnostic tools, e.g. psychological tests or neuroimaging methods - objectively assess the level of functioning of cognitive processes in a given person and thus propose the most optimal form of assistance.

Reference literature

Cierpiałkowska, L., Sęk H. (2016). Psychologia kliniczna. Warszawa: Wydawnictwo Naukowe PWN.
Herzyk, A. (2005). Wprowadzenie do neuropsychologii klinicznej. Warszawa: Wydawnictwo Naukowe „Scholar”.
Klasyfikacja zaburzeń psychicznych i zaburzeń zachowania w ICD-10 (1993). Kraków – Warszawa: Uniwersyteckie Wydawnictwo Medyczne „Vesalius”, Instytut Psychiatrii i Neurologii.
Kryteria diagnostyczne z DSM-5 (2013). Wrocław: Wyd. EDRA Urban & Partner. 
Maruszewski, T. (2015). Psychologia poznania. Gdańsk: Gdańskie Wydawnictwo Psychologiczne. 
Sapolsky, Robert M. (2012), Why Zebras Don’t Get Ulcers. Owl Book/Henry Holt and Co., 2004. 

About the author

Monika Mazur, MA – specialist in clinical psychology, psychotherapist, graduate of the Jagiellonian University Faculty of Philosophy. She has many years of experience working at the Józef Babiński Clinical Hospital in Kraków and at present she works at the Jagiellonian University Student Centre for Support and Adaptation and the Outpatient Mental Health Clinic.