Investigate a pseudoscientific belief and evaluate the evidence for and against, including a complementary or alternative therapy

What this dot point is asking

NESA wants you to use homeopathy (or another alternative therapy) as a case study of pseudoscience, evaluate the underlying claims against scientific evidence and discuss the public-health implications. Homeopathy is the canonical pseudoscience case study because it has been rigorously tested and conclusively refuted.

The answer

Homeopathy is a 220-year-old system of therapy founded by Samuel Hahnemann in 1796. It survives commercially despite the National Health and Medical Research Council's 2015 conclusion that there is no health condition for which homeopathy is effective.

Principles of homeopathy

1. Similia similibus curentur (like cures like)

A substance that causes symptoms in healthy people will cure those same symptoms in sick people. For example, since onions cause runny eyes, an onion-derived remedy is used for hay fever.

2. The law of infinitesimals

Diluting a remedy makes it more potent. The standard homeopathic dilution is 30C (1 part in 100, repeated 30 times). The final concentration is 1 in 10^60.

3. Succussion

Each dilution step must be followed by vigorous shaking against a leather pad to "potentise" the remedy.

The chemistry problem

Avogadro's number is approximately 6 × 10^23 molecules per mole. A typical homeopathic dilution of 30C (a 1:100 dilution applied 30 times) leaves a final dilution of 1 in 10^60. The probability that even a single molecule of the original substance remains in the bottle is essentially zero.

A useful comparison:

• A litre of any liquid contains at most about 10^25 molecules.
• A 30C dilution of any starting material would require diluting your remedy in a sphere of water as large as the Sun's orbit just to have one molecule of the original substance.
• Most homeopathic 30C remedies contain only water (or sugar in tablet form).

There is no active substance present. By the laws of chemistry, the remedy cannot work through pharmacological action.

The "water memory" defence

Defenders of homeopathy claim that water retains a "memory" of the substance it once contained. The original claim came from a 1988 paper by Jacques Benveniste in Nature. The paper was published with an unusual editor's note expressing scepticism. A team led by James Randi independently tested the claim and failed to replicate it. Nature published the failure to replicate in the same year. Benveniste's claim was retracted as a scientific result.

No mechanism for "water memory" is consistent with established chemistry: hydrogen bonds in water reorganise on a picosecond time scale, far too fast to retain any structural imprint of a dissolved substance over time.

The NHMRC 2015 review

In 2015 the Australian National Health and Medical Research Council conducted the most comprehensive evidence review of homeopathy to date.

Scope

Over 1,800 published studies across 68 medical conditions.

Methodology

Studies were graded for quality, with priority given to randomised controlled trials and systematic reviews.

Conclusion (verbatim)

"Based on the assessment of the evidence of effectiveness of homeopathy, NHMRC concludes that there are no health conditions for which there is reliable evidence that homeopathy is effective. Homeopathy should not be used to treat health conditions that are chronic, serious, or could become serious."

Policy responses

Following the NHMRC review:

• Private health insurance. Australian private health insurance ceased subsidising homeopathy from 2019.
• Pharmacy guidelines. The Pharmacy Board of Australia has discouraged pharmacists from recommending homeopathy.
• Medicare. Homeopathy is not a Medicare-funded service.
• TGA. Therapeutic Goods Administration requires homeopathic products to comply with labelling rules but does not regulate them as medicines.

Internationally, the UK NHS ceased funding homeopathy in 2018, France phased out reimbursement by 2021, and several other European systems have followed.

Why homeopathy still has supporters

Placebo effect

The placebo response is real and measurable. Patients given any treatment with confidence often report subjective improvement. This is particularly strong for pain and conditions with significant emotional or stress components.

Regression to the mean

People seek treatment when symptoms are worst. Statistical regression toward more normal symptoms over time will occur regardless of treatment.

Natural history of illness

Most acute conditions resolve on their own. Treatment timing coincides with natural resolution.

Consultation effects

Homeopathic consultations are typically 30 to 60 minutes long, allowing patients to feel heard, which has documented stress-reducing and self-regulatory benefits.

Confirmation bias

Successful outcomes are remembered and shared; failures are forgotten or attributed to "wrong remedy" choice.

These factors explain real reported benefits without requiring any chemical activity from the homeopathic remedies themselves.

Public-health risks

Homeopathy is not entirely harmless.

• Delay of effective treatment. Patients using homeopathy instead of proven treatment for serious conditions (cancer, infections, chronic disease) can suffer worsened outcomes.
• Children at particular risk. Several documented Australian cases of children dying from treatable infections while parents used homeopathy.
• Australian malaria homeopathy controversy. Some homeopaths have promoted homeopathic malaria prophylaxis to travellers, which is dangerous (NHMRC and TGA have warned against this).
• Resource diversion. Pharmacies stocking homeopathy implicitly endorse it, potentially confusing customers about what works.

Implications

Homeopathy is a textbook case study because:

1. The mechanism is chemically impossible.
2. Rigorous testing has been conducted.
3. The NHMRC has reached a definitive conclusion.
4. Policy has responded by reducing public funding.
5. Yet the industry continues to operate commercially.

This illustrates that pseudoscience can persist despite definitive scientific refutation, sustained by placebo effect, market demand and historical inertia.

Examples in context

Example 1. NHMRC 2015 homeopathy review methodology. The NHMRC review of homeopathy synthesised 1,800 papers across 68 clinical conditions, applying a structured quality assessment that down-weighted small trials, unblinded designs and trials with high risk of bias. The conclusion ("no condition for which there is reliable evidence that homeopathy is effective") was based on the absence of any condition where high-quality trials showed benefit greater than placebo. The methodology drew on internationally recognised systematic-review standards (PRISMA) and was reviewed by independent experts. The 2015 conclusion was reaffirmed by the European Academies' Science Advisory Council 2017 review and the Swiss Federal Office 2016 review, providing the strongest form of synthesis: replication across independent national reviews using different methodologies.

Example 2. TGA delisting of homeopathic products. In 2021 the Therapeutic Goods Administration removed homeopathic medicines from the Australian Register of Therapeutic Goods low-risk list. The regulatory change required vendors of homeopathic products to either provide evidence equivalent to other listed medicines (Level I trials) for any therapeutic claim, or remove the therapeutic claim. The change was contested by the homeopathy industry but supported by the NHMRC review and by patient-safety case-reports of harm from delayed conventional treatment. The case shows scientific consensus translating into regulatory action over a 20-year timescale, illustrating both how evidence-based policy works and how slowly it can act when the industry has commercial reach.

Try this

Q1. Explain why a 30C homeopathic dilution is unlikely to contain any molecule of the original substance. [3 marks]

• Cue. 30C is 1 part in 10 to the power of 60; Avogadro's number is about 6 times 10 to the power of 23; molecules of original substance vanish well before 12C.

Q2. A patient reports their chronic back pain improved after starting homeopathic treatment. Identify three non-causal explanations for the improvement. [3 marks]

• Cue. Placebo effect; regression to the mean (pain that prompted consultation likely to subside anyway); natural history of episodic back pain; co-treatment effects (rest, attention from a practitioner).

Q3. The TGA proposes requiring "no clinical evidence for any condition" warnings on homeopathic packaging. (a) State one ethical argument in favour. (b) State one practical objection. (c) Identify how an evidence-based policy framework could resolve the conflict. [2+2+2 marks]

• Cue. (a) Patient autonomy and informed consent. (b) Industry compliance cost and trade implications. (c) Weight evidence against industry interest; consult NHMRC and consumer-protection bodies; follow international precedent.