Children who experience severe deprivation early in life have smaller brains in adulthood, researchers have found.

The findings are based on scans of young adults who were adopted as children into UK families from Romania’s orphanages that rose under the regime of the dictator Nicolae Ceauşescu.

Now experts say that despite the children having been adopted into loving, nurturing families in the early 1990s, the early neglect appears to have left its mark on their brain structures.

“I think the most striking finding is … that the effects on the brain have persisted,” said Prof Edmund Sonuga-Barke, a co-author of the study from King’s College London, who added that the results showed neuroplasticity had limits.

“The idea that everything is recoverable, no matter what your experience … isn’t necessarily true – even with the best care you can still see those signs of that earlier adversity,” he said.

The plight of the undernourished children, who had little social contact and received insufficient care, shocked the world when it came to light after the fall of the communist government in 1989. Ceauşescu’s oppressive policies had banned abortion and contraception, while those without children were taxed. As a result, large numbers of children ended up in orphanages living in terrible conditions.

Previous studies involving the adoptees have shown they had marked cognitive difficulties as children – although these improved considerably into adulthood – while they also had high rates of conditions including attention deficit hyperactivity disorder (ADHD) and, as adults, high levels of anxiety and depression.

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Writing in the journal Proceedings of the National Academy of Sciences, Sonuga-Barke and colleagues told how they carried out brain scans and other measures of 67 Romanian adoptees who had spent between three and 41 months living in severe deprivation as children. At the time of the scans the adoptees were between 23 and 28 years old.

The team also took brain scans from 21 adults of a similar age who had been born and adopted in the UK before they were six months old.

The results revealed the Romanian adoptees had on average an 8.6% smaller brain overall than their UK peers. The team also found the size of the reduction was linked to the length of time spent in the Romanian orphanages: each additional month was linked to a 3cm3 lower total brain volume. “The more deprivation they had, the smaller their brains are,” said Sonuga-Barke.

The team’s analysis showed the smaller brain size explained the reduced IQ and, at least in part, the higher rates of ADHD found among the Romanian adoptees.

Among further findings, the team discovered that two areas of the brain showed a further size difference compared with the UK-born adoptees – although these did not vary with time spent in the orphanages.

Facebook Twitter Pinterest Local differences in adult brain structure associated with early deprivation. Photograph: Courtesy of King’s College London

One area, which included the right inferior frontal gyrus, was smaller in the Romanian adoptees even than expected from the reduced overall brain size. This area is a key centre for executive control circuits.

The second area, which included the right inferior temporal gyrus – an important area for auditory and visual processing as well as some aspects of memory – was larger than expected from the smaller brain size among the Romanian adoptees and appears to have provided a protective effect. The larger this area, the fewer the symptoms of ADHD in the Romanian adoptees. However, the team said it was not clear if this area grew in response to deprivation, or whether some children were, somewhat fortunately, predisposed to a larger area.

“I don’t think there is any better evidence in the whole of [human] neuroscience, for a compensatory effect in a high-risk sample like this,” said Sonuga-Barke. He added the team were surprised to find no particular impact on the amygdala – the region of the brain that processes emotions.

While the study cannot prove that early childhood deprivation leads to a smaller brain, Sonuga-Barke said it was likely, noting genetic influences, ethnic differences, overall body size, and effects in the womb had been ruled out as explaining the link.

The team proposed a number of possible mechanisms including the absence of experiences that are important for normal brain development, and chronic stress that could damage the developing brain.

However Sonuga-Barke said it remained unclear which features of deprivation were responsible, and that poor nutrition did not appear to explain the link.

“We are fairly confident that there are psychological routes to these effects as well, linked to lack of stimulation, lack of social interaction, and lack of attachment and bonding,” he said.

Prof Denis Mareschal, from Birbeck, University of London, said the study highlighted the importance of providing enriched environments in early infancy and childhood.

But he urged caution, noting the deprivation in the Romanian orphanages was extreme. “It remains to be seen whether less extreme deprivations typical of deprived upbringings in low socioeconomic status neighbourhoods in the UK would lead to similar long-term consequence on brain structure, or whether these milder forms of deprivations could be compensated for by subsequently experiencing enriched environments such as those provided by the Sure Start programmes here in the UK.”