Being able to think, remember, make decisions, and learn new things can often be taken for granted. However, these cognitive functions can be impacted by many different factors. This may include normal aging, diseases such as Alzheimer’s, or even reversible medication side effects.

What causes cognitive decline?
Understanding the various risks, influences, and direct causes of cognitive decline is vital to taking the first steps toward addressing concerns about cognitive health. These causes include:
- Age-related decline
- Neurodegenerative diseases
- Head injury
- Mental health conditions
- Genetic factors
- Vascular conditions
- Environmental causes
- Other reversible causes
If you are worried about the impact of cognitive decline, seek support from your healthcare provider. Your physician can thoroughly assess you and provide an accurate diagnosis and treatment plan. This article does not replace the need for professional medical advice.
Age-Related Cognitive Changes
When we think of difficulties with memory and other ‘thinking’ abilities, often the first thing that comes to mind is aging. Around 2 in 3 Americans will experience some amount of cognitive impairment in their lifetime, with an average age of onset at 70 years. [1]
Cognitive decline in the elderly
Changes in thinking are common for older people. This may include difficulty paying attention, slower name and word recall, and challenges with multitasking. Cognitive decline in older people happens due to changes to the brain that occur as we age. Some of these changes include: [2]
- Loss of communication pathways via neurons.
- Shrinkage of certain brain areas.
- Decreased blood flow to the brain.
- Damage from inflammation due to injury or disease.
While some changes in cognition are expected, more severe changes that affect a person’s ability to function in daily life are not part of normal aging. Such cognitive disorders require professional assessment, diagnosis, and treatment.
What are Neurodegenerative Diseases?
Neurodegenerative diseases represent the most common causes of significant cognitive impairment (otherwise known as dementia) in adults. They include diseases in which cells of the central nervous system (the brain and spinal cord) stop working or die. These conditions usually progress over time and have no known cure. [3] [4]
Alzheimer’s disease
It is estimated that 1 in 3 adults in the U.S. over the age of 85 years have Alzheimer’s disease, making it the single most common cause of dementia. Alzheimer’s disease involves structural changes to the brain that cause progressive memory loss, confusion, and other cognitive difficulties. As the disease progresses, it can affect an individual’s ability to learn new things, change their behavior, and eventually impact their speech and movement. [3] [5]
There is no cure for Alzheimer’s disease, but some medications have been shown to slow the progression of symptoms. Individuals affected may need increasing levels of support. [3] [6]
Lewy body dementia
Lewy body disease is another common cause of dementia. It occurs when abnormal proteins (called Lewy bodies) are deposited across the brain. These Lewy bodies can cause problems with thinking, movement, mood, and behavior. Lewy body dementia refers to the impact of Lewy body disease on a person’s cognition. [7]
Lewy body dementia is progressive, has no known cure, and may require increasing levels of support with daily functioning. When compared to Alzheimer’s disease, memory problems may not initially be apparent with Lewy body dementia. Equally, cognitive symptoms can be more unpredictable, and this disease may include the presence of behavioral disturbances and visual hallucinations. These differences can help physicians provide an accurate diagnosis. [7]
Parkinson’s dementia
Parkinson’s dementia is a form of cognitive decline often seen in people with Parkinson’s disease. Parkinson’s dementia is a neurodegenerative condition that causes uncontrollable movements (including stiffness and tremors) and difficulties with balance and coordination. These symptoms progress over time, and they frequently affect cognition, behavior, sleep, and mental health. [8]
Severe thinking and memory difficulties caused by the disease can often be made worse by the stress, depression, and medication side effects experienced by people living with Parkinson’s disease and related dementia. [8]
Traumatic Brain Injury and Cognitive Disorders
Neurodegenerative dementia is not the only cause of cognitive dysfunction. Severe head injuries can result in both short-term and long-term changes to brain function.
Short-term effects of head injuries
Mild head injuries can often result in temporary changes in cognition, which is frequently referred to as a concussion. These changes may include: [9]
- Cognitive symptoms – Difficulty concentrating, loss of short-term memory, or brain fog.
- Physical symptoms – Headache, visual problems, difficulty balancing, or immediate nausea and vomiting. These symptoms should improve rapidly.
- Behavioral symptoms – Anxiety, irritability, or feeling emotional.
- Sleep symptoms – Sleeping more or less than usual.
Symptoms should be mild and self-limiting. If they persist for more than a few days, seek help from your healthcare provider. However, the following red flags can indicate the presence of a more serious brain injury: [9]
- Seizures
- Repeated nausea and vomiting
- Inability to stay awake
- Slurred speech
- Worsening headache that does not go away
- Unequal pupil size or double vision
- Unusual or agitated behavior
If any of these red flag symptoms appear, seek immediate medical attention.
Long-term effects of head injuries
More serious brain injuries or repeated minor concussions can lead to long-term cognitive impairment. Traumatic brain injury can cause a wide variety of cognitive difficulties, including: [10]
- Difficulties with concentration, attention, and decision-making.
- Short and long-term memory problems.
- Difficulties with processing and acting on information.
- Problems with motivation and mental health.
- Difficulty speaking.
- Problems with reasoning, behavior, and self-awareness.
Psychiatric Conditions and Cognitive Function
Mental health plays an important part in cognitive function. Many common psychiatric conditions can impact the way an individual thinks and processes information.
Depression and cognitive function
Symptoms associated with cognitive disorders are often reported but rarely addressed in people with depression. Around 90% of those experiencing a depressive episode report symptoms of cognitive impairment. In fact, 40% of people report ongoing cognitive problems, even after remission of depressive symptoms. [11]
Depression should always be considered as a potentially reversible cause of cognitive decline in older adults. Diagnosis of cognitive impairment in people with depression remains challenging. Current treatment largely relies on existing medication and psychological therapies used for depression. [11]
Anxiety and cognitive function
Cognitive impairment has been well-documented in people suffering from specific anxiety disorders, such as obsessive-compulsive disorder (OCD) and post-traumatic stress disorder (PTSD). However, relatively little is known about the role of decreased cognitive function in generalized anxiety disorder (GAD), which is commonly referred to as anxiety. [12]
One 2013 study indicated that GAD is associated with cognitive impairment in executive functioning and long-term memory. However, subsequent research has shown a mixed picture, and more studies are needed to understand the true relationship between these conditions. [12] [13]
What is Vascular Cognitive Impairment?
Vascular cognitive impairment refers to a decline in mental functioning as a result of reduced blood flow to different areas of the brain.
Stroke-related cognitive decline
A stroke occurs when there is a blockage in (or, more rarely, bleeding from) the vessels supplying the brain, leading to the death of brain tissue. These areas of damage can result in a wide range of neurological deficits, including numbness, speech difficulties, and muscle paralysis. [14]
However, a stroke can also affect areas of the brain involved in language and cognition. Confusion and disorientation are common post-stroke changes. [14]
Vascular dementia
Vascular dementia describes a pattern of cognitive decline seen in other causes of dementia (such as Alzheimer’s disease), caused by diseases related to the blood vessels of the brain. Similarly, other causes of blood vessel narrowing or inflammation within the brain can also cause cognitive decline, as seen in some patients after a stroke. [14]
Are Cognitive Disorders Genetic?
Many cognitive disorders have a genetic component. This does not mean a person is guaranteed to develop cognitive decline if their parents did; however, the risk is increased in these people. Like other medical conditions, genetics combine with other health and lifestyle factors to determine the risk of developing a disease. [15]
Genetic risk factors for cognitive impairment
Some key genetic risk factors for developing dementia include: [15]
- Family history of dementia – Individuals with a parent or sibling affected by dementia are more likely to develop cognitive impairment. This risk is increased if multiple family members are affected.
- Risk genes – Some genes are associated with an increased risk of developing dementia.
- Deterministic genes – Very rarely, disruptions in certain genes have been found to directly cause cognitive disease. In Alzheimer’s disease, for example, less than 1% of those affected have a deterministic gene present.
Environmental Influences on Cognitive Health
Research into the role the environment plays in health is ever-increasing. Multiple studies have identified environmental factors that contribute to the development of cognitive decline.
Environmental risk factors for cognitive impairment
Some key environmental risk factors for the development of cognitive impairment include: [16]
- Fuel combustion from cars and factories
- Exposure to industrial particles
- Environmental pollution
- Poor indoor air quality
- Exposure to heavy metals in water
Reversible Causes of Cognitive Decline
So far, this article has discussed mostly permanent causes of cognitive impairment. However, it is equally important to be aware of several reversible causes. Cognitive decline in the elderly is often wrongly attributed to a neurodegenerative condition when, instead, a reversible explanation is present. [17]
Common reversible causes of cognitive impairment
Some of the most important reversible causes of cognitive decline include: [17]
- Medication side effects
- Substance abuse
- Nutritional deficiencies (most commonly vitamin B12)
- Thyroid problems
- Metabolic changes
- Infection
- Brain tumours
- Head injuries
Can You Prevent Cognitive Decline?
After exploring the causes of cognitive impairment, you may be wondering what can be done to prevent this decline. Several risk factors, such as genetics and age, cannot be modified. As with other diseases, it is impossible to fully prevent cognitive disorders.
Lifestyle modifications to prevent cognitive decline
However, there are some important lifestyle changes that have been shown to reduce your risk of developing neurodegenerative dementia: [18]
- Engage in regular physical activity (at least 150 minutes at moderate intensity per week)
- Avoid smoking
- Limit alcohol consumption to mild-moderate use only
- Consume a balanced, high-quality diet (particularly a form of Mediterranean diet)
- Participate in regular cognitive activities (as a way of keeping the mind active)
Managing cognitive health once diagnosed
If a loved one has been diagnosed with a form of cognitive impairment, there are several valuable strategies you can use to support them. Your healthcare provider should be able to make recommendations that suit your situation. Here are some strategies commonly used to optimize health: [19]
- Behavioral therapies – Participate in activities that increase social interaction and improve mood.
- Avoid stressful problems – Adapt communication and a person’s living environment to prevent distress.
- Promote self-care – Make necessary modifications that allow a person to maximize their own abilities.
- Maintain physical mobility – Engage in programs that optimize strength and mobility.
- Maintain cognitive function – Make use of suitable activities, such as puzzles or word games.
- Hale, J. M., Schneider, D. C., Mehta, N. K., & Myrskylä, M. (2020). Cognitive impairment in the U.S.: Lifetime risk, age at onset, and years impaired. SSM – Population Health, 11(100577). https://pmc.ncbi.nlm.nih.gov/articles/PMC7153285/
- How the Aging Brain Affects Thinking. (2023, June 27). National Institute on Aging. https://www.nia.nih.gov/health/brain-health/how-aging-brain-affects-thinking
- Alzheimer’s Association. (2024). What Is Alzheimer’s Disease? Alzheimer’s Disease and Dementia. https://www.alz.org/alzheimers-dementia/what-is-alzheimers
- National Cancer Institute. (2019). NCI Dictionary of Cancer Terms. Cancer.gov. https://www.cancer.gov/publications/dictionaries/cancer-terms/def/neurodegenerative-disorder
- Hebert, L. E., Weuve, J., Scherr, P. A., & Evans, D. A. (2013). Alzheimer disease in the United States (2010-2050) estimated using the 2010 census. Neurology, 80(19), 1778–1783. https://www.neurology.org/doi/abs/10.1212/wnl.0b013e31828726f5
- Alzheimer’s Association. (2019). Treatments. Alzheimer’s Disease and Dementia. https://www.alz.org/alzheimers-dementia/treatments
- What Is Lewy Body Dementia? Causes, Symptoms, and Treatments. (n.d.). National Institute on Aging. https://www.nia.nih.gov/health/lewy-body-dementia/what-lewy-body-dementia-causes-symptoms-and-treatments#types
- National Institute on Aging. (2022, April 14). Parkinson’s Disease: Causes, Symptoms, and Treatments. https://www.nia.nih.gov/health/parkinsons-disease/parkinsons-disease-causes-symptoms-and-treatments
- CDC. (2024, May 16). Signs and Symptoms of Concussion. HEADS UP. https://www.cdc.gov/heads-up/signs-symptoms/index.html
- HeadWay. (2024). Cognitive effects of brain injury. https://www.headway.org.uk/about-brain-injury/individuals/effects-of-brain-injury/cognitive-effects-of-brain-injury/
- Perini, G., Cotta Ramusino, M., Sinforiani, E., Bernini, S., Petrachi, R., & Costa, A. (2019). Cognitive impairment in depression: recent advances and novel treatments. Neuropsychiatric Disease and Treatment, 15, 1249–1258. https://pmc.ncbi.nlm.nih.gov/articles/PMC6520478/
- Wang, Y., Yang, Y., Zhang, X., Zhu, Y., Dai, Y., & Liu, T. (2015). Cognitive impairment in generalized anxiety disorder revealed by event-related potential N270. Neuropsychiatric Disease and Treatment, 1405. https://pmc.ncbi.nlm.nih.gov/articles/PMC4461089/
- Tempesta, D., Mazza, M., Serroni, N., Moschetta, F. S., Di Giannantonio, M., Ferrara, M., & De Berardis, D. (2013). Neuropsychological functioning in young subjects with generalized anxiety disorder with and without pharmacotherapy. Progress in Neuro-Psychopharmacology and Biological Psychiatry, 45, 236–241. https://www.sciencedirect.com/science/article/abs/pii/S0278584613001176
- Alzheimer’s Association. (2019). Vascular Dementia. Alzheimer’s Disease and Dementia. https://www.alz.org/alzheimers-dementia/what-is-dementia/types-of-dementia/vascular-dementia
- Alzheimer’s Association. (2024). Causes and Risk Factors. Alzheimer’s Disease and Dementia. https://www.alz.org/alzheimers-dementia/what-is-alzheimers/causes-and-risk-factors
- Luo, H., Hu, H., Zheng, Z., Sun, C., & Yu, K. (2024). The impact of living environmental factors on cognitive function and mild cognitive impairment: evidence from the Chinese elderly population. BMC Public Health, 24(1). https://bmcpublichealth.biomedcentral.com/articles/10.1186/s12889-024-20197-2
- Bello, V. M. E., & Schultz, R. R. (2011). Prevalence of treatable and reversible dementias: A study in a dementia outpatient clinic. Dementia & Neuropsychologia, 5(1), 44–47. https://pmc.ncbi.nlm.nih.gov/articles/PMC5619138
- National Institute of Health. (2020, June 17). Combination of healthy lifestyle traits may substantially reduce alzheimer’s. https://www.nih.gov/news-events/news-releases/combination-healthy-lifestyle-traits-may-substantially-reduce-alzheimers
- Logsdon, R. G., McCurry, S. M., & Teri, L. (2021). Evidence-Based Interventions to Improve Quality of Life for Individuals with Dementia. Alzheimer’s Care Today, 8(4), 309. https://pmc.ncbi.nlm.nih.gov/articles/PMC2585781/
Our Medical Affairs Team is a dedicated group of medical professionals with diverse and extensive clinical experience who actively contribute to the development of our content, products, and services. They meticulously evaluate and review all medical content before publication to ensure it is medically accurate and aligned with current discussions and research developments in mental health. For more information, visit our Editorial Policy.
MentalHealth.com is a health technology company guiding people towards self-understanding and connection. The platform provides reliable resources, accessible services, and nurturing communities. Its purpose is to educate, support, and empower people in their pursuit of well-being.

Olly is a medical writer with 7+ years of experience in clinical medicine. He holds a Bachelor of Medicine and Surgery and a Bachelor of Medical Science.
Jennie Stanford is a dual-board certified physician in both family medicine and obesity medicine, holding an MD, FAAFP, and DipABOM. She has experience in both clinical practice and peer-quality reviews.
Our Medical Affairs Team is a dedicated group of medical professionals with diverse and extensive clinical experience who actively contribute to the development of our content, products, and services. They meticulously evaluate and review all medical content before publication to ensure it is medically accurate and aligned with current discussions and research developments in mental health. For more information, visit our Editorial Policy.
MentalHealth.com is a health technology company guiding people towards self-understanding and connection. The platform provides reliable resources, accessible services, and nurturing communities. Its purpose is to educate, support, and empower people in their pursuit of well-being.