Sleep has a major impact on our health and wellbeing. Busy lifestyles often make it difficult to sleep as much as we would like to. Not sleeping enough affects our mood, ability to focus, and risk of many medical conditions.

We are often encouraged to sleep more, but can sleeping too much also be unhealthy?

We asked 26 experts in sleep research and neurobiology whether too much sleep is bad for you, 85 percent said 'no'. Here is what we found…

What is the data on hours of sleep and health?

There have been numerous research papers looking at the relationship between sleep time and different medical outcomes.

Dr Jo Caldwell, an expert from the U.S. Naval Medical Research Unit in Neuropsychology, summarizes the results of these papers: "The optimal amount of sleep seems to be about 7 solid hours. For each hour below that amount, there are additive adverse health consequences, and for each hour above the 7 hours there are additive adverse health consequences."

These 'adverse health consequences' include many lifestyle diseases, such as diabetes, heart disease, and obesity. Oversleeping, combined with low physical activity, is also correlated with increased mortality.

It is important to remember that all this data is observational. That means it is collected by observing people who have different sleep patterns and measuring their health outcomes.

Currently, there is no experimental data – where sleep duration is experimentally increased – that links oversleeping with mortality. Actually, the experimental result is the opposite.

Dr Monika Haack, an expert in sleep research at Harvard University, says, "Extending habitual sleep duration has a beneficial effect on a number of biological systems, e.g., blood pressure decreases, sensitivity to pain decreases, and insulin sensitivity improves."

What is the link between oversleeping and poor health?

As shown above, observational data suggests that sleeping for much longer than 7 hours is correlated with negative outcomes.

Dr Jamie Zeitzer, an expert in sleep research from Stanford University, says, "The problem with interpreting this as 'long sleep is bad for you' is that we don't know why the long sleepers have bad outcomes. It might be that they are sleeping a long time because there is something medically wrong that induces great sleep (sleep is great for fixing things)."

Many of the experts agreed that there may be other factors linking long sleeping times with negative outcomes, but it is not clear what these factors are.

Dr William Killgore, an expert from Arizona University, says "The most likely explanation for the associations with long sleep is that the disease state is what leads to excess sleep, probably not the other way around. But without prospective experimental evidence, it remains a bit of a chicken-and-egg question."

How much sleep is healthy?

Thankfully, we don't need to worry about sleeping too much. Dr James Ware, an expert from Eastern Virginia Medical School, says "It is not possible for a healthy person to 'overdose' on sleep. The person will instead lie awake, usually uncomfortably, in bed or get up."

Each person requires a different amount of sleep to function normally. Dr Vivien Abad, an expert from Stanford University, suggests that "for most adults, we recommend 7-8 hours of sleep. The key message is to get enough sleep to fulfil your health needs. Your ability to remain alert and functional the entire day especially after meals is a good indicator of adequacy of hours of sleep."

Finally, you can use a change in your sleep pattern to help detect changes in your health.

Dr Killgore explains, "If you find you are needing a lot more than 7-hours to function effectively, or if the amount of sleep you need has increased significantly, it might be something to bring up with your doctor. The increased sleep itself may not be hurting you, but it might be telling you that something else is."

The takeaway

Oversleeping is unlikely to negatively impact your health. On the other hand, needing to sleep more than usual may be an indicator that you need to talk to your doctor.

Article based on 26 expert answers to this question: Is too much sleep bad for you?

This expert response was published in partnership with independent fact-checking platform Subscribe to their weekly newsletter here.