Dr. Georgia Zara of the University of Turin and Dr. David Farrington of the University of Cambridge say that the protective effect seems to wear off after the age of 21.
Their findings are based on a study, published online in Springer's Journal of Youth and Adolescence, which explored whether or not certain childhood factors delay the onset of criminal behavior until adulthood.
Zara and Farrington followed a total of 400 males in London, who took part in The Cambridge Study in Delinquent Development, between the ages of 8 to 10 and 48 to 50.
The researchers divided the subjects into three groups: 35 late onset criminals first convicted at 21 years old or older with no overt signs of delinquency at ages 10 to 14 and 15 to 18; 129 early offenders first convicted between the ages of 10 and 20 years old; and 236 law-abiding men.
They observed that nervous and withdrawn boys were generally shielded against committing criminal acts during adolescence, but that effect disappeared after the age of 21.
Compared with early onset offenders, late onset criminals were more nervous, had fewer friends from ages 8 to 10, and were less likely to have had sexual intercourse by the age of 18.
Those who turned to crime later in life were more anxious at school from ages 12 to 14 and very neurotic by age 16, compared with non-offenders.
Based on their observations, the researchers came to the conclusion that adult offending could be predicted from childhood, and might shed light on early psychological and temperamental traits likely to play a role in delaying criminal behavior until adulthood.
According to the researchers, their findings might be helpful in studying how kids with such characteristics might find themselves in high-risk situations later in their lives, being unprepared to cope with the pressures and difficulties of adult life.
They say that it could be very beneficial to tackle the issues involved in delayed criminal behavior early.
"Given that diverse strongest predictors of adult criminality in this study can be addressed (e.g., nervousness), kept under control (e.g., anxiety), or modified (e.g., not having had sexual intercourse), they imply possible targets for successful intervention. Hence, there is enormous scope for significant cost savings, both economically and in the quality of life, from early intervention policies," write the authors.
A research article on the study has been published in the Journal of Youth and Adolescence.