# Can Untreated Mental Illness Cause Dementia-Like Symptoms?
When someone starts having trouble remembering things or struggles to focus, the first thought is often that dementia might be developing. However, the reality is more complicated. Several mental health conditions can create symptoms that look remarkably similar to dementia, a condition sometimes called pseudodementia. Understanding this distinction matters because many of these conditions are treatable, and catching them early can prevent serious complications.
Depression stands out as one of the most common culprits. Severe depression can present with cognitive problems that mimic dementia so closely that doctors need to carefully evaluate patients to tell them apart. When depression goes untreated, it can cause confusion, difficulty concentrating, and memory problems that interfere with daily life. The good news is that once depression is identified and treated, these cognitive symptoms often improve significantly.
Anxiety is another mental health condition that can create dementia-like symptoms. Excessive worry and fearfulness can make it harder for people to think clearly and remember information. Sleep problems often accompany anxiety, which compounds the cognitive difficulties since poor sleep quality directly affects thinking and memory.
One particularly important treatable condition is obstructive sleep apnea. While not strictly a mental illness, untreated sleep apnea frequently causes cognitive problems that resemble early dementia. In the short term, disrupted sleep makes it harder to think clearly, and people may struggle with attention, multitasking, reaction time, and memory. Doctors often see patients in their 50s and 60s who report memory problems and mental fog, and in many cases, the main cause is untreated sleep apnea rather than a permanent form of dementia. The encouraging part is that treating sleep apnea can significantly improve thinking and memory in these individuals.
Over time, repeated drops in oxygen and poor-quality sleep from untreated sleep apnea may cause lasting changes in the brain. Research shows a strong link between untreated sleep apnea and a higher risk of all types of dementia, including Alzheimer’s disease and vascular cognitive decline. However, because sleep apnea is reversible and treatable, it is an important condition to evaluate in anyone experiencing cognitive changes.
Why does this matter so much? Early evaluation helps determine what is actually happening and how best to support the patient. When mental health conditions go undiagnosed and untreated, people miss out on opportunities for intervention and treatment. This increases the burden on both patients and caregivers. Families lose time to process and adapt to potential new roles as caregivers, and caregivers who have more time to prepare often feel more competent in their role and experience fewer psychological problems of their own.
Additionally, untreated conditions can lead to worse outcomes overall. Research suggests that those with undiagnosed cognitive problems experience worse hospitalization outcomes and have more 30-day readmissions than their peers with a formal diagnosis. Without treatment interventions and supports that often come with a formal diagnosis, untreated conditions can incur more costs through more frequent emergency room visits and preventable hospitalizations.
The key takeaway is that cognitive changes should not automatically be assumed to be dementia. Mental health conditions like depression and anxiety, along with treatable medical conditions like sleep apnea, can create symptoms that look like dementia but may improve with proper treatment. This is why getting evaluated early is so important. A healthcare provider can help rule out reversible causes of cognitive impairment and create targeted care plans based on what is actually causing the symptoms.
Sources
https://www.archbold.org/articles/2026/january/how-to-spot-signs-of-mental-illness-in-the-elder/
https://creyos.com/blog/early-detection-for-dementia-care
https://www.sheernesshealthcentre-drpatel.nhs.uk/Library/Conditions/Articles/alzheimers-disease
https://www.thebrf.org/understanding-depression-in-dementia/
https://drsagnikmukherjee.com/blog/identifying-dementia-early/