Mental Illness and Dementia: The Link Families Should Know About (and What to Do Next)

If someone you love has lived with schizophrenia, bipolar disorder or depression and is now becoming forgetful, it is natural to wonder whether the two are connected. They can be, but most people with a mental illness never develop dementia. A 2024 study using Welsh health records and UK Biobank data found that dementia was diagnosed more often after schizophrenia (hazard ratio 2.87), bipolar disorder (2.80) and depression (1.63), with no clear link for anxiety. The harder question is a practical one: how do you tell new memory problems from the existing illness, and what care covers both? This guide explains.

*Last reviewed: 11 November 2026. Sources include BMJ Mental Health, BJPsych Open and NICE. This is general information and does not replace advice from a GP, psychiatrist or nurse.

Does Mental Illness Increase the Risk of Dementia?

Research says the risk is higher, though not inevitable. The BMJ Mental Health study concluded that psychiatric disorders are associated with an increased risk of later dementia, with greater risk for more severe disorders.

A hazard ratio of 2.87 means a higher chance over time, not certainty. Many people with schizophrenia or bipolar disorder live into old age without dementia. The study shows an association and does not prove one condition causes the other.

For families, the useful message is vigilance, not alarm. If memory or thinking changes appear, ask for them to be assessed rather than assuming they are part of the existing illness.

Why Is Dementia Harder to Spot When Someone Already Has a Mental Health Condition?

Because the signs overlap with what is already known. Withdrawal, suspicion, low motivation and poor concentration can come from depression, psychosis, medication or dementia, so changes are easily put down to the existing illness.

Clues that deserve a medical review include forgetting recent events while remembering old ones, getting lost in familiar places, struggling with tasks someone managed before, and a shift from their usual pattern of symptoms.

NICE's dementia guideline says people with distressing symptoms should be assessed for physical health, depression, possible undetected pain, medication side effects, their personal history and the environment. Ask the GP to consider both mental health and cognition together, and keep a dated diary of changes to take with you.

How Does Physical Health Complicate the Picture?

Older adults with severe mental illness tend to have more physical health problems. A BJPsych Open study of 4,175 people over 60 in south-east London found hospital admissions for physical illness at 5.15 times the rate of the general population, with longer hospital stays.

In practice, new confusion in this group may come from infection, constipation, pain or a medication effect, not only from dementia or relapse. A sudden change needs prompt medical assessment, because delirium can look like a worsening of mental illness.

That is why care for someone with both conditions needs regular physical checks alongside attention to mood and memory.

How Do Medicines Need Extra Care When Both Conditions Are Present?

Medicines deserve particular attention. NICE advises that antipsychotics should only be offered to people with dementia who are at risk of harming themselves or others, or who are severely distressed by agitation, hallucinations or delusions. The benefits and harms should be discussed with the person and their family, the lowest effective dose used for the shortest time, and the need reviewed at least every six weeks.

NICE also warns that for people with Lewy body dementia or Parkinson's disease dementia, antipsychotics can worsen movement symptoms and sometimes cause severe sensitivity reactions.

If someone has taken medication for a mental illness for years, do not stop or change it without specialist advice. Ask for a medication review whenever a diagnosis of dementia is made or suspected.

What Does Good Care Look Like When Someone Has Both?

Good care treats the whole person, with both conditions in view. It starts with someone who knows the full history, including past illness, what helped, and what triggers distress.

In daily life, that means consistent staff, a predictable routine, and communication adapted to memory loss. It means watching mood and thinking separately, so a dip in one is not blamed on the other, and giving meaningful activity within a person's current abilities. It also means involving the GP, the community mental health team and the family in reviews.

Our guide to what a residential mental health care home involves explains this side of support, and our article on dementia and end-of-life care covers what comes later.

When Is a Care Home the Right Step, and What Should You Ask?

Consider a care home when safety at home becomes uncertain, when symptoms prove hard to manage without round-the-clock support, or when a carer feels exhausted. If you remain unsure, a short respite stay can help you see how someone settles.

Ask whether staff hold training in both dementia and mental health, and how the home works with psychiatrists and community mental health teams. Find out how doctors review medicines, how staff monitor physical health, and how the team responds to distress, hallucinations or paranoia. You should also check whether younger and older residents live together and how the team manages that.

Read the latest inspection report on the Care Quality Commission website, ask the home how it has responded to any findings, and visit more than once.

How Does Cedar Lodge Support People Who Need Dementia and Mental Health Care in Taunton?

Cedar Lodge is a residential care home on the northern outskirts of Taunton, overlooking Taunton Green, supporting older people and younger adults living with dementia and mental health conditions. Alongside it, The Limes is a purpose-built recovery and rehabilitation centre for up to 15 people with a range of mental health conditions.

Residents can take part in an activities programme that includes life history and reminiscence work, and spend time in the sensory gardens. You can read about specialist dementia care, the home in Taunton, or browse all our care.

Frequently Asked Questions

Does schizophrenia or bipolar disorder increase the risk of dementia?

Research shows a higher risk, around 2.8 to 2.9 times in a 2024 UK study, but most people with these conditions do not develop dementia.

Can depression be mistaken for dementia?

They can overlap, because depression can affect concentration and memory. A proper assessment should consider both.

Is it safe to give antipsychotics to someone with dementia?

Only in specific circumstances. NICE says they should be offered only if there is a risk of harm or severe distress, at the lowest dose for the shortest time, and reviewed every six weeks.

Who should assess someone with a mental health condition who may have dementia?

Start with the GP, who can refer to a memory service or older adults' mental health team. Ask for mental health and cognition to be reviewed together.

Can one care home support both dementia and mental health needs?

Some can. Ask about staff training, access to psychiatric support, medication reviews and physical health monitoring.

If you are caring for someone with both memory and mental health needs, you do not have to work it out alone. Please call the team at Cedar Lodge on 01823 286158. We are happy to listen, answer questions and show you around whenever you feel ready.