"Follow the money" is the rule in politics for figuring out the real reason something not quite logical is happening.

It appears to apply as well to the overdrugging of California foster youths, based on the latest in Bay Area News Group reporter Karen de Sá's ongoing series, "Drugging Our Kids" — an analysis using both data and individuals' stories to illuminate the use of pharmaceuticals to control the behavior of foster children.

Consumer advocates, lawmakers and the California Medical Board are taking this seriously.

In earlier reports, de Sá exposed the use of powerful psychotropic drugs on foster children — often to control kids' behavior rather than because of a clinical diagnosis. Side effects such as lethargy and massive weight gain can damage kids' lifelong health and their ability to get an education.

Most doctors receive money or gifts from drugmakers for various reasons including travel, speaking engagements and drug trials. This is not illegal. But de Sá's investigation found that from 2010 to 2013, prescribers of psych medications in the foster care system received more than twice as much as typical California doctors. And last year, doctors who prescribed the most on average to foster youths accepted almost four times as much as those in a lower-prescribing group.

The implication of preying on the most vulnerable of patients to boost drug sales is hard to discount.

State Sens. Jim Beall, D-San Jose, and Holly Mitchell, D-Los Angeles, have called on Health Care Services Director Toby Douglas to release more complete information about doctors prescribing and children taking psych drugs. It would include numbers of foster children on multiple medications and high doses, as well as children being given drugs for "conduct disorders."

Consumer Watchdog's Carmen Balber told de Sá that her group has suspected that payments by drugmakers influence prescribing practices — "But this investigation was particularly disturbing because of the patients it affects. The conflict of interest is clear in these cases, and we think that action is long overdue."

The state medical board is investigating practices in treating foster youths exposed in de Sá's earlier reports. Now it will look at prescribing patterns to see if they are unethical.

High prescribers have received more than $10,000 a year on average from drug companies. And some other excesses stand out. A Sacramento doctor received more than $310,000 in speaker fees over four years. Drug marketers know that doctors listen to other doctors.

Foster children's lives are controlled by the state. The system is supposed to look out for them, but the human services agencies directly responsible for these children are failing them. Lawmakers and regulatory agencies need to step up. We will continue watching.