While most older people who develop problems with their memory and thinking that are severe enough to impair their ability to function in everyday life typically, are found to have Alzheimer’s disease or other neurodegenerative diseases, some have an undiagnosed and treatable psychiatric disorder masquerading as dementia. These conditions including depression can affect memory and thinking and, when severe, create a clinical picture similar to dementia. This phenomenon, known as “pseudodementia”, is encountered in clinical practice. It is important to identify because it may be reversible with appropriate treatment.

There is controversy about what the longer-term prognosis is for people diagnosed with pseudodementia. This has implications for how to manage patients, what advice to give to patients and their family, and how to conceptualise the disorder. Some studies found that people with pseudodementia eventually develop organic dementia, so called pseudo-pseudodementia. To address this, we conducted a systematic review of studies that had been conducted on pseudodementia and which followed up patients over time.

Eighteen studies followed patients from several weeks to 18 years. Overall, patients with pseudodementia were at greater risk of later developing organic dementia. Importantly, not all patients did; many patients remained stable or improved, albeit some still impaired by their psychiatric disorder. Our review showed possible treatment benefits and differences with age; patients diagnosed with pseudodementia at a younger age had better outcomes.

Finally, people with apathy (which is the commonest behavioural symptom in dementia) can be misdiagnosed as having depression, so called pseudo-depression and then often treated for the wrong condition. Patients with apathy do not respond to antidepressants.

Receiving the correct clinical diagnoses are crucial to patients receiving the correct treatment for their condition. A missed diagnosis of a potentially reversible depressive pseudodementia can have tragic consequence for the patient and family.

Recent research has neglected the study of pseudodementia. Our findings reveal a clear need for better diagnostic skills, further research with modern investigative tools, such as neuroimaging and genetic sequencing, and clinical trials to better understand underlying mechanisms and determine effective treatment strategies.