A Canadian study has showed that childhood poverty and stress as an adult leave an imprint on a person's genes, providing an insight into how environmental influences get under the skin.

The study, published last week in a special volume of the Proceedings of the National Academy of Sciences, looks at how experiences beginning before birth and in the years after can affect the course of a person's life.

Known as epigenetics, or the study of changes in gene expression, this research examined a process called DNA methylation where a chemical molecule is added to DNA and acts like a dimmer on a light bulb switch, turning genes on or off or setting them somewhere in between.

The research team discovered that childhood poverty, rather than socioeconomic status as an adult, was correlated with the marks or methylation patterns left on genes.

"We found biological residue of early life poverty," said Michael Kobor, whose lab leadd the research, adding that this was based on clear evidence that environmental influences correlate with epigenetic patterns.

In addition, the researchers found the amount of stress hormones produced by adults was also linked with variations in DNA methylation.

However, it is unknown whether increased stress as an adult could leave marks on DNA or whether the marks may play a role in the amount of stress hormones released, according to Kobor.

The study is jointly conducted by the University of British Columbia and the Centre for Molecular Medicine and Therapeutics.