雅思阅读 144: The Chemical Imbalance That Wasn't（被推翻的"化学失衡"理论）

改编从 Psychology Today / Molecular Psychiatry（Moncrieff et al., 2022）。雅思阅读 Section 3 难度，约 1050 词。 素材来源：https://www.psychologytoday.com/au/blog/side-effects/202207/decisive-blow-the-serotonin-hypothesis-depression

Reading Passage

A. Ask almost anyone on the street what causes depression and a familiar answer will follow: the brain runs short of a chemical called serotonin, a "chemical imbalance" that medication then corrects. Surveys suggest that between eighty-five and ninety percent of the public holds precisely this belief, and among psychology students interviewed a decade ago, nearly half had first heard the explanation from a physician. Yet the theory behind the conviction is far shakier than its popularity implies. It was first proposed in 1965 by a Harvard psychiatrist, who suggested that low levels of the neurotransmitter might underlie low mood. In the decades that followed, the idea was simplified, repeated and amplified — until, stripped of every qualification, it hardened into a piece of folk wisdom about mental illness. That such a thin scientific idea could settle so deeply into public consciousness is, in itself, a story worth telling. It is also a story that a major review, published in 2022, was finally prepared to challenge directly, asking whether the evidence for the theory had ever been as strong as the advertising suggested. It is worth dwelling on how odd this gap was: a belief held by nearly the whole population, propagated through the most intimate conversations of medicine, yet resting on an idea that serious researchers had doubted for decades.

B. Much of the theory's public power came not from laboratories but from marketing. As advertising for antidepressant pills flooded magazines and television in the early 2000s, two researchers asked a pointed question: did the claims made in these advertisements actually match the published science? Their answer, published in a leading medical journal, was a flat no. Regulators had permitted drug companies to phrase their claims only in the subjunctive — depression "may" be due to a serotonin deficiency, and the drugs were "presumed" to work by boosting the chemical — yet the advertisements routinely dropped the hedges and sold certainty instead. Even some psychiatrists privately admitted the gap. One prominent editor confessed on national radio that he explained the treatment to patients as correcting a serotonin shortage not because the evidence convinced him, but because patients wanted to hear that their doctor understood what he was doing. The polite fiction, he acknowledged, concealed an honest uncertainty about how the medicine actually worked. He was far from alone; behind the reassuring phrase spoken in countless consulting rooms lay a genuine gap that marketing had long since papered over.

C. It took a comprehensive review to put the popular version on trial. Led by a psychiatrist at University College London, the 2022 analysis drew together the largest meta-analyses and systematic reviews on the subject, covering tens of thousands of participants, and asked a blunt question: is depression genuinely associated with lower serotonin? Its conclusion was striking. Across the main lines of research — measurements of serotonin itself, of its breakdown products, of its receptors and of the transporter protein that antidepressants target — the reviewers found no consistent evidence that depressed people had less of the chemical. Some studies, if anything, hinted at the opposite: slightly more serotonin activity in patients, a pattern the authors suspected was the residue of long-term antidepressant use rather than a cause of illness. The "chemical imbalance" that the public understood so confidently was, on this reading, a story the data had never actually told. What made the finding striking was not that researchers had proved depression was caused by too much serotonin, but that after decades of searching they had failed to find the simple deficiency everyone assumed was there.

D. Two further lines of evidence weakened the hypothesis. In one kind of experiment, researchers artificially lowered serotonin in hundreds of healthy volunteers by depriving their diets of the amino acid needed to make it. If low serotonin truly produced depression, these volunteers ought to have sunk into gloom; they did not reliably do so. In the other, very large genetic studies compared the genes of depressed and well people, looking especially at the gene for the serotonin transporter. No meaningful difference emerged, and the once-popular claim that a certain gene variant combined with stress to cause depression was effectively ruled out. What did emerge instead was far less glamorous. When the reviewers examined life experience, they found that stressful events exerted a powerful and predictable effect: the more of them a person had weathered, the greater the risk of becoming depressed. Cause, it seemed, was more likely to live in the world than in a single molecule. None of this showed that depression was imaginary, or that suffering patients had invented their illness; it showed only that a cheap and familiar explanation had outrun the evidence on which it was built.

E. The implications reach well beyond the laboratory. Prescriptions for antidepressants have climbed steeply since the 1990s; in England, roughly one in six adults now receives them in a given year. The authors argued that patients should not be told they suffer from low serotonin, nor that the drugs work like insulin does for diabetes — a comparison they called actively misleading, because no one yet understands precisely what the medicines do to the brain. None of this means the drugs are useless, or that sufferers are imagining their illness. It means the simple chemical story, however comforting, has outlived its evidence. Treating a disorder as complicated as depression as nothing more than a missing ingredient, the reviewers warned, not only misdescribes the problem but also denies patients the chance to weigh uncertain benefits against real side effects. A more honest account, they suggested, would begin with the stressful, social and biological forces that the data actually support, and stop pretending a single neurotransmitter could bear the whole weight of the explanation. Whether such honesty will change how millions of people understand their own illness, however, is a question that the published science alone cannot settle.

Questions 1-4

Choose the correct heading for paragraphs B, C, D and E from the list of headings below.

List of Headings i. How advertising turned a hedge into certainty ii. What the largest review actually found iii. Why the theory appeals to psychiatrists iv. Experiments and genes that failed to confirm the theory v. The public health stakes of a discredited story vi. The discovery of serotonin in the brain vii. How antidepressants are manufactured

1. Paragraph B: ____
2. Paragraph C: ____
3. Paragraph D: ____
4. Paragraph E: ____

Questions 5-8

Choose the correct letter, A, B, C or D.

5. What did surveys suggest about public belief? A. Most people disbelieve the chemical imbalance idea. B. Most people believe low serotonin causes depression. C. Most people have never heard of serotonin. D. Most people refuse antidepressants.

6. What did the two researchers conclude about SSRI advertising? A. It was fully supported by the science. B. It overstated claims that regulators had allowed only as possibilities. C. It caused people to abandon treatment. D. It was banned by regulators.

7. According to the 2022 review, studies of serotonin receptors and transporters found A. clear proof that depressed people have less serotonin activity. B. weak, inconclusive evidence and even hints of higher activity. C. that receptors do not exist in the human brain. D. that antidepressants have no effect at all.

8. What did the life-event analysis find? A. Stressful events had little effect on depression risk. B. Experiencing more stressful events raised the risk of depression. C. Only genetic factors predicted depression. D. Stress protected against depression.

Questions 9-13

Do the following statements agree with the claims of the writer?

Write:

• TRUE if the statement agrees with the information
• FALSE if the statement contradicts the information
• NOT GIVEN if there is no information on this

9. The serotonin hypothesis was first put forward in 1965.
10. Regulators insisted that all antidepressant advertisements make absolute claims.
11. Artificially lowering serotonin reliably made healthy volunteers severely depressed.
12. The serotonin transporter gene differed clearly between depressed people and controls.
13. The review team was led by researchers based at Harvard University.

Questions 14-15

Complete the summary below using NO MORE THAN TWO WORDS from the passage.

By depriving volunteers of the amino acid needed to make serotonin, researchers performed tryptophan (14) _____________ experiments, which did not reliably produce low mood. Meanwhile, stressful (15) _____________ were found to exert a strong effect on the risk of depression.

答案与解析

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