The effect of cannabis in the womb was studied
Smoking cannabis while pregnant could harm the developing foetal brain, researchers have claimed.
The team at the University of Aberdeen also said certain prescribed drugs, including some to treat obesity, could have an effect in the womb too.
The work focuses on the importance of molecules produced naturally in the brain, and how certain nerve cells recognise and connect with each other.
Anything that affects this could affect brain function, it was claimed.
The brain molecules called endocannabinoids are said to function in a similar way to tetrahydrocannabinol (THC) from cannabis, targeting the same receptors and signalling systems in the brain.
The researchers said this signalling process should occur unhindered for the brain to develop normally.
Prof Tibor Harkany, recruited to the University of Aberdeen as part of the Scottish Universities Life Sciences Alliance (Sulsa), said: "Our findings highlight that the integrity of this signalling system should be maintained and not disrupted if the brain is to develop normally.
"Anything that disrupts this process such as cannabis smoking or certain drugs that interfere with this signalling system could ultimately affect the brain's functionality."
Jan Mulder, first author of the study and Alzheimer's Research Trust fellow at the University of Aberdeen's Institute of Medical Sciences, said: "Our initial findings showed the importance of these naturally occurring molecules in guiding the growth and connections of nerve cells in the developing brain.
"Now we demonstrate the extent of this signalling system and that complex network of neurons - the backbones of higher cognitive functions - do not develop normally when endocannabinoid signalling is disturbed."
Cannabis is viewed as among the more widely used drugs by women at reproductive age.
Previous research has claimed that babies born to mothers who took cannabis while they were pregnant went on to experience problems with physical activity.
The new research - an experimental study involving mice - is published in the Proceedings of the National Academy of Sciences of the United States of America (PNAS).