Rule #1. Establish your credentials. You need to have lots of letters after your name. It doesn’t really matter what they mean, so long as they sound impressive. It’s also good to be a fellow of some kind of Royal Society. Some of these are rather snooty and appoint fellows by an exclusive election process, but it’s a little known fact that others require little more than a minimal indication of academic standing and will admit you to the fellowship provided you fill in a form and agree to pay an annual subscription. So sign up as a Fellow of the Royal Society of Medicine, and keep good company with a range of naturopaths, homeopaths and chiropracters who have discovered this easy route to eminence. The really nice thing is that even academics can be hoodwinked by this one.
Rule #2. Find a controversial topic. This is key. You have to be willing to take a definite position on something that people have strong views about. A scare story is good - we’ve all been doing X for years but it could damage us. Finding someone to blame is also good - people who do Y are feckless. And the buzz word of the decade is neuroscience, so if you can work that in, success is guaranteed. If you're short of ideas, the list of the right might help inspire you. A recent article in the Biologist hits the spot with “The biological effects of day care”, managing to get us worried about an everyday activity, blame working mothers, and get in a neuro message all at once. It's even spiced up with a bit of conspiracy theory: experts know that day care is bad for children’s brains but nobody is allowed to speak out because it is too politically sensitive. This presses so many buttons that few journalists could resist the story.
Rule #3. Specify a causal chain. As we shall see when it comes to assembling evidence, it is particularly useful to have a causal chain with several steps. For instance:
The point here is that if you can usually find at least some studies that provide evidence for bits of the causal chain. Although it may be inconvenient if, as in this case, studies looking for a link between A and D fail to come up with clear evidence (Lucas-Thompson et al, 2010), you can rely on two things: first, few readers will be familiar with the research literature, so they will only know as much as you tell them. And second, step C, brain abnormality, is highly salient and once you start talking about that, it will distract attention from the other levels of description.
Rule #4. Avoid rigorous peer review. You don’t want to have your views critiqued by someone who knows the literature, or checks your sources. Writing books is a safe bet for avoiding pre-publication scientific critique. As far as journals go, the Biologist is ideal. This publication for the members of the Society of Biology claims to be peer-reviewed, but, as we shall see, the review process is far from rigorous.
Rule #5. Assemble supportive evidence. Note, it is important not to present all relevant studies, just those with findings that can be fitted into the causal chain.
The author of the paper in question, Dr Aric Sigman, presents us with so much positive evidence that he manages to give the impression that the whole casual chain has been validated. He starts by mentioning studies that investigated the link between A and B and find that salivary cortisol is increased in the afternoons in children attending day care. This is a product of the hypothalamo-pituitary-adrenal (HPA) axis, which is elevated in response to stress. This result is well-established, both from studies comparing groups of children who do and don’t attend day care, and from comparing the same children on days when they stay at home or go to day care. This is a potentially concerning finding, if it can be shown that there are consequences for children’s learning and behaviour. As Sigman notes “Of central concern is that the routine stress experienced at day care could cause permanent changes in the child’s neuroendocrine networks, with long-term consequences for their mental and physical health as adults.” (p. 30). The article that he cites does discuss this issue, but notes the complexity of causal relationships and cautions against assuming that the cortisol elevation is harmful. In fact the authors draw attention to an animal study suggesting a very different conclusion:
“As in the work on cortisol responses to fullday child care, these separations in squirrel monkey infants produced marked and repeated activations of the HPA axis. However, followed into the late juvenile and early adult age, animals exposed to this form of early life stress were found to be less fearful, to produce lower rather than higher cortisol responses to stressors, and to show more optimal development of prefrontal regulatory brain circuits; consistent with these findings, they also performed better on tests of executive functioning. Thus, at least for this animal model, repeated separation stress early in life fostered a form of resilience.” Gunnar et al (2010) (my emphasis)
Sigman avoids mentioning any of this and turns instead to look at the links between cortisol levels and ill health, starting with studies that show a link between cortisol and cardiovascular disease. He does not explain that these were done on people aged over 65 years, but rather implants in people’s minds the notion that this is relevant for his arguments about daycare in toddlers. Next comes the serious stuff: research linking elevated cortisol to the brain. We are told that “Cortisol is considered neurotoxic and has a global impact on cerebral size (e.g. McEwen 2007; Sheline 2003).” (p. 29). Again, we are left with the distinct impression that children who attend day care will have small brains, but to find out what actually is meant here we need to read the cited articles. When we do, we find that McEwen (2007) is a thorough research review of the physiology and neurobiology of stress and adaptation that nowhere mentions the terms ‘neurotoxic’, ‘global’ or ‘cerebral size’. Rather, in this article McEwen develops a complex theory that considers both positive and negative impact of stress. It actually has a section subtitled “Protection and damage: the two sides of the response to stressors” which discusses animal studies demonstrating how elevated cortisol can either improve or interfere with brain function, depending on context. Neurotoxicity does feature in the other article, by Sheline (2003), but this is concerned with mood disorders in adults, and discusses effects of hypercortisolemia, a condition where there is chronic elevation of cortisol, rather than a temporary increase at specific times of day. Subsequent citations are to papers that considered the role of cortisol in psychiatric disorders such as anxiety and depression: note that now the evidence is focused on a link between cortisol and adult psychiatric disorders in the opposite direction (from D to B), yet it is presented in the context of discussing consequences of high cortisol in children who attended day care. Sigman further states: “a higher cortisol awakening curve may be a biological marker for an underlying disposition towards developing depressive and anxiety disorders” (p. 30), even though the studies of toddlers attending day care show a cortisol response that develops through the day, rather than a chronically raised level: see Vermeer and van IJzendoorn (2006) for a well-balanced discussion of such evidence.
It would be tedious to wade through every cited article, but it’s worth considering just one more example. We are told “In human grey matter, the quality of a mother’s care in early childhood is thought to alter the size of the hippocampus (Buss et al, 2007)” (p. 30). Erm no. Buss et al clearly stated there were no differences in left or right hippocampal volume between those categorised as having high or low maternal care. What they did find was a complicated interaction between birth weight, gender and maternal care, such that birth weight predicted hippocampal volume only in female subjects reporting low maternal care. But even this limited result doesn’t support Sigman’s case. We are talking about ‘low maternal care’, not ‘attendance at daycare’. And guess what? When we look at ‘low maternal care’ we find it measured from a self-report questionnaire, where low care is partly identified in terms of maternal overprotection. Those categorised this way were more likely to have endorsed items describing their mother in such terms as:
- Tended to baby me
- Tried to make me feel dependent on her
- Felt I could not look after myself unless she was around
- Was overprotective of me
Rule #6. Anticipate criticism but don't let it worry you. People who actually do research in the area you are reviewing may get irritated, but most scientists in the field wouldn’t bother on the grounds that they don't know who you are, and aren’t interested in pursuing academic debates outside the domain of mainstream journals. The worst you may get is a few nerdy bloggers such as Gimpy or Mind Hacks criticising you for lack of scholarship, sensationalism and cherrypicking of evidence. Or, if you're really unlucky, you might be up against Ben Goldacre on Newsnight. But meanwhile, your purpose as celebrity scientist has been achieved: your views are all over the media.
Gunnar MR, Kryzer E, Van Ryzin MJ, & Phillips DA (2010). The rise in cortisol in family day care: associations with aspects of care quality, child behavior, and child sex. Child Development, 81 (3), 851-69. PMID: 20573109
Lucas-Thompson, R. G., Goldberg, W. A., & Prause, J. A. (2010). Maternal work early in the lives of children and its distal associations with achievement and behavior problems: A meta-analysis. Psychological Bulletin, 136(6), 915-942. DOI: 10.1037/a0020875
McEwen, B. S. (2007). Physiology and neurobiology of stress and adaptation: Central role of the brain. Physiological Reviews, 87(3), 873-904.doi: 10.1152/physrev.00041.2006 (Open Access)
Sigman, A. (2011). Mother superior? The biological effects of day care. The Biologist, 5 (3), 29-32.
Vermeer, H. J. & van IJzendoorn, M. H. (2006). Children's elevated cortisol levels at daycare: A review and meta-analysis. Early Childhood Research Quarterly, 21(3), 390-401.doi 10.1016/j.ecresq.2006.07.004