Is It Depression or Dementia? Memory Problems in Later Life

Depression in older adults often shows up as poor concentration, slow thinking and forgetfulness, which can look a lot like early dementia. The two also travel together: depression can be an early sign of dementia and raises the risk of it. A good assessment looks at mood as well as memory, and depression is very treatable at 75, just as it is at 35.

Why does depression look like dementia?

Depression isn't only sadness. In later life it often shows up as flatness, tiredness, losing interest in things and a thinking speed that's turned down a few notches. If you can't concentrate, information never gets stored properly, so it seems "forgotten."

Older adults also tend to describe the physical side (sleep, appetite, aches) rather than say they feel low. So the family notices forgetfulness, the GP hears "I'm tired," and the mood part slips through.

How can you tell them apart?

There's no single tell, but some patterns lean one way or the other.

People whose memory trouble is mostly driven by depression often complain loudly about their memory and say "I don't know" quickly, without really trying. In early Alzheimer's it's more common for the person to downplay problems while the family worries, and to give a wrong answer confidently.

Timing helps too. A drop in mood that comes first, often after a loss, an illness or a move, points toward depression. Slowly building memory problems with mood changes following later point the other way.

In practice, doctors often can't be sure on the first visit. They'll treat the depression and see what the thinking does afterwards. If memory clears up as mood lifts, that's a strong answer. If it doesn't, more testing follows.

Can you have both?

Yes, and it's common. Somewhere around a third of people with Alzheimer's have significant depressive symptoms at some point. The 2024 Lancet Commission on dementia counts depression as a modifiable risk factor, while also noting that depression in later life can be one of the first signs of brain changes already under way.

That's why the old idea of "pseudodementia," memory problems that are purely depression and fully go away, has fallen out of favour. Some people in that group do develop dementia later, so it's worth keeping an eye on things after recovery. Our post on mild cognitive impairment explains what that in-between zone looks like.

What should you ask the doctor?

Ask for a mood screen alongside any memory test. Short questionnaires like the Geriatric Depression Scale take a few minutes. Also ask about:

• Blood tests for thyroid, B12 and other things that affect both mood and thinking
• A review of all medications, since some cause fatigue or low mood
• Hearing and vision, which feed into isolation
• Whether a referral to a memory clinic or old-age psychiatry makes sense

If you've been using an online memory test at home, bring the results, but don't let a good or bad score replace a proper conversation.

What helps?

Treatment works in older adults. Talking therapies, antidepressants chosen with age in mind, physical activity and regular social contact all have evidence behind them. Loneliness is a big driver of late-life depression, and we've written about what reconnects people.

If someone you love has gone quiet and forgetful, don't assume it's "just ageing" or that it's definitely dementia. It might be depression, and that's a door you can actually open.