Associations between parenting behavior and anxiety in a rodent model and a clinical sample: relationship to peripheral BDNF levels.

Early care, anxiety and a possible biological signal across species

Can research in animals and people reveal related patterns between early caregiving, anxiety and brain-related biology? This study combined a rat experiment with an adolescent sample to examine BDNF, a protein involved in the development and adjustment of connections between nerve cells.

Two approaches to the same question. Rat mothers received limited nesting material or standard conditions during their offspring’s early life. Researchers observed maternal behavior and later tested anxiety-like behavior in the adult offspring, measuring BDNF in blood and several brain regions. In the human part, 129 adolescents were assessed for anxiety symptoms, perceived parental care, blood BDNF and a variation in the BDNF gene called Val66Met.

The animal findings linked altered care with later anxiety. Under the limited-nesting conditions, mothers showed more contact that lacked active caregiving behaviors. Their adult offspring showed more anxiety-like behavior and higher blood BDNF. The amount of this maternal contact was also associated with adult blood BDNF.

In adolescents, greater maternal warmth was associated with fewer symptoms of separation anxiety, social phobia and school phobia. Maternal overprotection was associated with higher blood BDNF only among carriers of the Met version of the gene. The human result therefore depended partly on genetic background.

These observations suggest that BDNF measured outside the brain may mark some processes associated with early experience and anxiety. They do not show that a higher blood level means more or less BDNF activity in a particular brain region, or that BDNF caused the anxiety differences.

The value of the combined approach is that controlled animal work and human observational data can inform the same developmental question. Their findings are related, but the caregiving measures and outcomes are not identical across species. Further work is needed to determine what circulating BDNF reflects and whether it helps explain, rather than merely accompanies, the behavioral patterns.