Researchers have found a significant increase in the number of online search queries for 'insomnia' when governments around the world implemented stay-at-home orders in response to the Covid-19 pandemic outbreak.

The results, published in the Journal of Clinical Sleep Medicine, there were 2.77 million Google searches for insomnia in the US for the first five months of 2020, an increase of 58 per cent compared with the same period from the previous three years.

While searches for insomnia trended downward from January through March 2020, consistent with prior years, they surged upward in April and May 2020.

This increase also was associated with the cumulative number of Covid-19-related deaths in the spring.

"I think it's safe to say, based on our findings as well as those from survey studies showing an increased level of insomnia symptoms in certain populations, that a lot of people were having trouble sleeping during the first months of the pandemic," said lead author Kirsi-Marja Zitting from the Brigham and Women's Hospital in the US.

Insomnia involves difficulty falling asleep or staying asleep, or regularly waking up earlier than desired, despite allowing enough time in bed for sleep.

The researchers analysed Google search data in the US and worldwide between January 1, 2004, and May 31, 2020.

Consistent with prior years, searches for insomnia in 2020 occurred most frequently during typical sleeping hours between midnight and 5 a.m., peaking around 3 a.m.

"This is the prime time for sleeping, so all these people were awake and probably wondering why they couldn't sleep," said Zitting.

Due to concern about the potential long-term impact of the pandemic on sleep quality, the researcher said that she plans to continue tracking searches for insomnia.

"While acute insomnia, typically triggered by stress or a traumatic event, will often go away on its own, I am worried that the longer this pandemic drags on, the greater the number of people who go on to develop chronic insomnia," Zitting said.

"And unlike acute insomnia, chronic insomnia can be difficult to treat," she added.