Playing video games can alter the visual perceptions of gamers, a study has found.
Researchers at Nottingham Trent University looked at the after-effects of playing video games.
The study found many gamers saw distorted versions of real world surroundings following play.
Some reported seeing video game menus 'pop up' in front of their eyes while in conversation with friends, while others said they had seen coloured images and HUDs (head-up displays) when driving.
Others struggled to sleep while some suffered flashbacks after game play.
The study, led by psychologists Angelica Ortiz de Gortari and Professor Mark Griffiths, looked at gamers' perceptual experiences, referred to as Game Transfer Phenomena (GTP).
It analysed experiences given by 483 gamers on 54 online video game forums.
The researchers concluded that intensive play can result in misperceptions and visual distortions of real-life objects and environments and pseudo-hallucinatory experiences with video game content.
The study found GTP could occur while gaming, immediately after play or after some delay.
Visual illusions are known to be able to easily trick the brain, and staring at visual stimuli can cause 'after-images' or 'ghost images'.
But the researchers found evidence that GTP was triggered by associations between video game experiences, and objects and activities in real life contexts.
In some playing experiences, video game images appeared without awareness and control of the gamers, and in some cases, the images were uncomfortable, especially when gamers could not sleep or concentrate on something else.
These experiences also resulted in irrational thoughts such as gamers questioning their own mental health or getting embarrassed.
Ortiz de Gortari said: "Visual experiences identified in GTP show us the interplay of physiological, perceptual and cognitive mechanisms and the potential of learning with video games even without awareness.
"It also invites us to reflect about the effects of prolonged exposure to synthetic stimuli."
She said the psychological profile of the gamers in the study is unknown because the data was collected in online game forums.
"However, different gamers reported similar experiences in the same games. This highlights the relevance of the video games' structural characteristics but gamers' habits also appear to be crucial," she added.
Professor Griffiths said: "Some gamers may be more susceptible than others to experience GTP. The effects of these experiences appear to be short-lived, but some gamers experience them recurrently.
"More research is needed to understand the cognitive and psychological implications of GTP.
"This study shows there is a need to investigate neural adaptations and after-effects induced by video game playing as a way of encouraging healthy and safe video game playing. "
The study has been published in the International Journal of Human-Computer Interaction.