Tag Archives: Adolescents

Childhood Decline in Physical Activity

Previously we have seen evidence from a cohort of children and adolescents in Norfolk that the decline in physical activity among modern young people takes place after childhood and during adolescence.[1] However in the majority of studies, including that which we looked at, the estimates of activity are largely based on reports. Now comes a new paper from Farooq and colleagues using objective measurements based on an accelerometer.[2] This new study shows that the previous conclusion was probably wrong. The study shows that there is a decline in moderate to vigorous physical activity throughout childhood and adolescence. A further interesting finding is that this study, based on objective measurements of activity, did not replicate the prevailing view that energy expenditure declines more rapidly in girls than in boys. This paper has considerable implications for policy. I would like to thank Professor Jeremy Dale for bringing this important paper to my attention.

— Richard Lilford, CLAHRC WM Director

References:

  1. Corder K, van Sluijs EMF, Ekelund U, Jones AP, Griffin SJ. Change in children’s physical activity over 12 months; longitudinal results from the SPEEDY study. Pediatrics. 2010; 126(4): e926-35.
  2. Farooq MA, Parkinson KN, Adamson AJ, et al. Timing of the decline in physical activity in childhood and adolescence: Gateshead Millennium Cohort Study. Br J Sports Med. 2017.
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Legalisation of Marijuana

Having borne down heavily on tobacco, it seems like everyone is now campaigning to make marijuana legal – are they mad?

A libertarian would say that there is no case to ban tobacco (or effectively ban it by draconian taxes on consumption). All tobacco can do is kill you, and as long as you know this you may use it. Marijuana is a different case altogether. It appears that it does not just kill you, it maims you – and not just your body, but you – your personality, your memory, your intelligence, i.e. your essence. And it is particularly attractive to teenagers – those with the most precious and vulnerable brains. Use is increasing in the US and has increased in association with decriminalisation, even if cause and effect is hard to prove.[1] Meanwhile a recent longitudinal cohort study found that persistent cannabis dependence was linked to downward socioeconomic mobility, financial difficulties, workplace problems, and relationship conflict.[2] It gets worse, the concentration of psycogenic compounds is increasing in the plant due to selective breeding. The attitude and fashion among liberal metropolitans “tobacco is vulgar, but marijuana is cool.” Have we gone mad? If we could confine the need to people over 18, and campaign against it, then over time we could reduce use. But a chemical that actually alters the structure of the adolescent brain and is more ubiquitous than boxing? We urgently need more information on the effects legalising cannabis has on usage. Also, more research on its effects on the brain using functional MRI. I wonder if Mendelian randomisation could shed light on causality?

— Richard Lilford, CLAHRC WM Director

References:

  1. Azofeifa A, Mattson ME, Grant A. Monitoring Marijuana Use In the United States: Challenges in an Evolving Environment. JAMA. 2016; 316:1765-6.
  2. Cerdá M, Moffitt TE, Meier MH, et al. Persistent Cannabis Dependence and Alcohol Dependence Represent Risks for Midlife Economic and Social Problems: A Longitudinal Cohort Study. Clin Psychol Sci. 2016; 4(6): 1028-46.

 

Adverse Effects of Well-Intentioned Interventions to Improve Outcomes in Adolescence

We recently reported on the evaluation of a study to reduce aberrant teenage behaviour that had a negative effect – i.e. it actually increased the behaviour it was designed to prevent. On further enquiry, it turns out that this is but one of a series of studies targeting adolescent behaviour, that showed effects opposite to those intended.[1] The classic study, quoted by Dishion, McCord & Poulin, was the Cambridge-Sommerville Youth Study.[2] [3] This was a randomised study of matched pairs of adolescent boys (irrespective of previous behaviour) in a run-down neighbourhood. The intervention consisted of visits (an average of twice a month) by counsellors who also took the boys to sporting events, gave them driving lessons, and helped them and their family members apply for jobs. The intervention had harmful effects on arrests, alcohol problems, and mental hospital referral on follow-up 40 years later.[4] [5] In a sub-group comparison, boys sent to summer school more than once had a particularly bad outcome. This is consistent with the theory that mutual interaction reinforces behaviour problems among susceptible adolescent boys.

On the basis of this RCT and other randomised studies, one of which was cited in the previous post, “there is reason to be cautious and to avoid aggregating young high-risk adolescents into intervention groups.” Apparently interventions targeted at parents are more positive in their effects. CLAHRC WM has a large theme of work on adolescent health and the Director invites comments from inside and outside our organisation.

— Richard Lilford, CLAHRC WM Director

References:

  1. Dishion TJ, McCord J, Poulin F. When Interventions Harm. Peer Groups and Problem Behaviour. Am Psychol. 1999; 54(9): 755-64.
  2. Healy W, & Bronner AF. New Light on Delinquency and its Treatment. New Haven, CT: Yale University Press. 1936.
  3. Powers E, & Witmer H. An Experiment in the Prevention of Delinquency: The Cambridge-Sommerville Youth Study. New York: Columbia University Press. 1951.
  4. McCord J. A Thirty-Year Follow-Up of Treatment Effects. Am Psychol. 1978; 33: 284-9.
  5. McCord J. Consideration of Some Effects of a Counseling Program. In: Martin SE, Sechrest LB, Redner R (Eds.) New Directions in the Rehabilitation of Criminal Offenders. Washington, D.C.; The National Academy of Sciences. 1981. p.394-405.