Wednesday February 27 2008
The behaviour of adolescents and their parents was assessed
Teenage anger has been linked to the size of a part of the brain called the amygdala, The Times reported yesterday. Using scans of adolescent brains, researchers have shown, the newspaper says, that “the length and intensity of their tantrums correlates directly with the size of their amygdalas".
The newspaper report is based on a study that filmed 137 adolescents having argumentative discussions with their parents and then used brain scans using MRI technology to examine the size of different regions in the brain. The researchers found that an increase in size of the amygdala, a region known to be involved with emotions and memory, was linked to a longer duration of anger. The study also found that in boys the smaller left anterior cingulate cortex, thought to be involved with thinking and decision making, was linked with whining and being more anxious. However, only a small number of adolescents were included in this study; more research involving larger numbers of people is needed to show a convincing link between differences in the size of particular brain regions and mood or mental health.
Where did the story come from?
This research was carried out by Sarah Whittle and colleagues of the ORYGEN Research Centre, University of Melbourne, Australia and the Oregon Research Institute, USA. The study was supported by the ORYGEN Research Centre and the Colonial Foundation, and by various postgraduate awards, fellowships and scholarships of the researchers. It was published in peer-reviewed medical journal Proceedings of the National Academy of Sciences.
What kind of scientific study was this?
This was an experimental imaging study. The authors looked at the effect that brain structure has on day-to-day moods in adolescents. The researchers recruited 137 male and female adolescents (aged 11 to 14) from schools in Australia who were part of a larger developmental study. All were free from depression, substance abuse or eating disorders.
All participants and their parents took part in a 20 minute videotaped problem-solving interactions (PSI) activity. Five topics on which they held conflicting views were discussed (such as lying and answering back), as these were likely to provoke negative behaviour. Experienced observers used a system to code each time the participant’s mood or behaviour changed during the confrontation (e.g., the participant became angry or started whining). The verbal content of their speech was also monitored for changes (e.g., provocation or approval). The codes were then grouped together to provide an overall pattern of behaviour, such as aggression or moodiness. The assessors determined the average duration of the behaviour and assessed whether certain stimuli (e.g., parental aggression) provoked a particular sequence of behaviour.
The researchers then carried out brain imaging (MRI) scans on the adolescents to look at the size of three key regions of the brain involved with mood regulation: the amygdala, the anterior cingulate cortex (ACC) and the orbitofrontal cortex (OFC). They used statistical analyses to look at the relationships between brain size, the duration of aggressive behaviour and the response to parental mood change. They also looked at the differences between boys and girls, as previous research has demonstrated gender differences in brain development and mood behaviours.
What were the results of the study?
The researchers found that gender had no effect on the duration of aggressive behaviour. They found a positive relationship between the duration of aggression and the size of the left and right amygdala, but this was only significant on the left-hand side.
There were differences between boys and girls when they looked at the relationship between aggression duration and size of the ACC. In boys, longer periods of aggression were linked with greater asymmetry in the structure of the paralimbic ACC, with a reduction in size on the left. There was no relationship between OFC size and the duration of aggression.
When the researchers looked at the patterns of change in the adolescents’ moods in response to their parents, they only found a significant link with OFC size among boys. Greater receptivity to the parents’ moods was linked to a smaller volume of the left OFC.
What interpretations did the researchers draw from these results?
The authors say that their findings suggest that mood behaviour and the ability to control it during family interactions is related to brain structure. They note that their findings during adolescence, a period of rapid brain development, may have implications for mental health in later life.
What does the NHS Knowledge Service make of this study?
This is a complex imaging study in a small number of adolescents. The researchers have found some links between the structure of regions of the brain and their observations during recorded parental conflict. However, only limited conclusions can be drawn from these results.
- The findings cannot prove causation; that is, they cannot say whether mood behaviour is caused by, or predicted by, the size of brain regions, or whether the size change occurs as a result of mood behaviour.
- It is not possible to say whether adolescence has an effect on both brain structural development and moody or aggressive behaviour. Comparison with other age groups would be worthwhile.
- The sample size is small and a much larger study would be needed to provide more meaningful conclusions, particularly to see whether there are any true differences between males and females.
- The conflict situation is only experimental. Having a videotaped discussion in a false setting may not reflect normal, every-day situations or how “moody” or “aggressive” an individual is for most of the time or with people other than their parents.
- The suggested link to later mental health conditions is only speculative and has not been assessed.
This study will likely require further research to examine the relationship between brain structure and size, and mood or mental health behaviours. However, even if the size of different brain regions is related to anger and emotion in humans, it is likely that current behavioural and psychological treatments, such as counselling, will remain useful.
Sir Muir Gray adds...
I am not clear how parents could use this information.