Natural health products are naturally occurring, nonprescription substances that promote or preserve good health, according to Health Canada. They include vitamins and minerals, herbal remedies, traditional and homeopathic medicines, and probiotics. As the list of available natural health products is extensive, only commonly used products with a reasonable body of published data are reviewed.
5.7. What Is St. John’s Wort? How Effective Is St. John’s Wort for the Treatment of MDD?
St. John’s wort (SJW)
(Hypericum perforatum) is a perennial plant that has been used as a herbal medicine for many centuries, with the total extract (which include hypericin/hyperforin and several other flavonoids) being regarded as active. Suggested mechanisms of antidepressant action include direct effect on serotonin receptors, monoamine oxidase inhibition, and neuroendocrine and ion channel modulation.
58,59 Formulations of SJW have varied widely, as has the dose range (500 to 1800 mg/day), while treatment duration has spanned 4 to 12 weeks.
58,60Since 2009, 2 systematic reviews
60,61 have confirmed the comparable efficacy of SJW to antidepressants and superiority to placebo for mild to moderate MDD (Suppl. Table S6). In MDD of greater severity, 1 systematic review
60 found SJW to be of equal efficacy to selective serotonin reuptake inhibitors, with a lower rate of withdrawals due to adverse events, whereas the other
61 reported no difference between SJW and placebo. In 2 subsequent RCTs, one found no significant difference between SJW, sertraline, or placebo monotherapy,
62 while the other found SJW monotherapy superior to placebo, particularly for individuals with moderate levels of atypical depression.
63Although SJW is significantly better tolerated than many first-line antidepressants,
64 side effects include gastrointestinal upset, headaches, skin irritation, photosensitivity, and dry mouth.
65 There is concern that higher potency extracts can interfere with the metabolism of various medications.
66 In addition, serotonin syndrome and hypomania have been reported when SJW is used concurrently with antidepressants.
67,68SJW is recommended as first-line monotherapy in mild to moderate MDD (Level 1 Evidence) and is recommended as a second-line adjunctive treatment for moderate to severe MDD (Level 2 Evidence) (
Table 3).
5.8. What Are Omega-3 Fatty Acids? How Effective Are Omega-3 Fatty Acids for the Treatment of MDD?
Omega-3 fatty acids (ω-3 fatty acids) are polyunsaturated fatty acids that are primarily found in oily fish and certain nuts and seeds. Different formulations of ω-3 fatty acids have been studied, the most common being eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The typical dose range is 3 to 9 g/day of ω-3 or 1 to 2 g of EPA plus 1 to 2 g of DHA per day.
69 Duration of treatment ranges from 4 to 16 weeks.
70,71Four new meta-analyses
70-73 and 2 systematic reviews
69,74 have provided updates on the efficacy of ω-3 fatty acids in MDD (Suppl. Table S7). One reported no benefits (13 trials,
N = 731),
70 another meta-analysis (25 trials,
N = 1438)
72 and 1 review
74 reported equivocal outcomes, 1 meta-analysis (15 trials,
N = 916) reported a positive outcome as monotherapy,
73 and 1 meta-analysis (11 trials,
N = 418)
69 and 1 review
71 reported a positive outcome as adjunctive therapy.
Contradictory findings may be due to differences in study populations, methodology, and intervention parameters. The most recent and rigorous meta-analysis (11 trials,
N = 418),
71 reporting specifically on DSM-defined MDD, found large effect sizes for the efficacy of ω-3 fatty acids. The variability in findings may also be due to differences in the composition and dosage of ω-3 fatty acids used. Two meta-analyses
71,73 found that EPA-dominant formulations were superior to DHA-based options for alleviation of depressive symptoms.
The ω-3 supplements are generally well tolerated with only mild side effects, including diarrhea, nausea, and a fishy aftertaste.
11,75 Patients on anticoagulant and antiplatelet medications may also require additional monitoring.
76 Manic induction has been reported in a few cases, although not in bipolar depressed patients.
77,78Thus, ω-3 fatty acids have Level 1 Evidence of efficacy but, because of the inconsistency in the evidence, are recommended as second-line monotherapy for mild to moderate MDD and adjunctive to antidepressants for moderate to severe MDD (
Table 3).
5.9. What Is SAM-e? How Effective Is SAM-e for the Treatment of MDD?
SAM-e is a natural substrate in the human body, including in the brain, that is thought to function as a methyl donor in various physiological processes.
61 Proposed mechanisms of antidepressant action include modulation of monoaminergic neurotransmission.
79SAM-e is prescribed in Europe as an oral or parenteral treatment for several conditions, including MDD.
80 In the United States and Canada, SAM-e is available as an oral over-the-counter dietary supplement, often used in the dose range of 800 to 1600 mg/day given in divided doses with meals over 4 to 12 weeks.
81 Studies have also used intravenous and intramuscular formulations of SAM-e, at doses of 200 to 400 mg/day across 2 to 8 weeks,
61,81 which may be more effective than oral supplements.
69Two systematic reviews found SAM-e effective as a monotherapy versus placebo in mild to severe MDD
61 or versus comparator antidepressants in mild to moderate MDD
81 (Suppl. Table S8). There is also evidence to support adjunctive SAM-e with antidepressants in mild to moderate MDD.
69,81 There are concerns, however, about trial methodologies and paucity of data on SAM-e as maintenance therapy.
61Overall, SAM-e is relatively well tolerated, with the most common side effects being gastrointestinal upset, insomnia, sweating, headache, irritability, restlessness, anxiety, tachycardia, and fatigue.
11,81In summary, SAM-e is recommended as a second-line adjunctive treatment for use in mild to moderate MDD (Level 1 Evidence) (
Table 3).
5.10. What Is DHEA? How Effective Is DHEA for the Treatment of MDD?
Dehydroepiandrosterone (DHEA) is a hormone produced by the adrenal cortex, which is subsequently converted to sex hormones in the body.
82 It plays a role in modulating neuroendocrine and immune homeostasis and influences monoaminergic and glutaminergic neurotransmission.
83 Dosage of DHEA commonly used in research ranges from 30 to 450 mg/day, with treatment lasting 6 to 8 weeks.
11 No new clinical trials have been conducted since 2009 that specifically evaluated the efficacy of DHEA in treating MDD, and therefore, there is no new evidence to assess.
Side effects of DHEA include hirsutism, acne, hypertension, liver damage, and manic induction.
84 Higher doses are also associated with more serious adverse effects, such as worsening of prostatitis and increased risk of breast cancer.
84DHEA remains recommended as a third-line treatment with Level 2 Evidence as monotherapy and Level 3 Evidence as adjunctive treatment (
Table 3).
5.12. What Other Natural Health Products Have Been Evaluated in the Treatment of MDD?
Several other natural health products have been evaluated as potential treatments for depression (
Table 3). Only the evidence for relatively better evaluated agents (folate preparations, inositol, acetyl-L-carnitine,
C. sativus [saffron],
Lavandula [lavender], and
R. rosea [roseroot]) was reviewed (Suppl. Table S10).
A meta-analysis (11 trials,
N = 2204) of folic acid found no evidence to support its efficacy as a short-term adjunctive agent for antidepressants, although many subjects had medical and other psychiatric comorbidities.
89 However, 2 narrative reviews
90,91 and a retrospective analysis
92 support the use of folate preparations (particularly L-methylfolate) as monotherapy
90 or adjunct to antidepressants for MDD,
90-92 although small samples and the lack of double-blind, placebo-controlled trials are notable limitations. Genetic polymorphisms may also play a role in efficacy, and certain folate preparations may be better suited to specific genetic profiles.
90There was no evidence from a meta-analysis (9 trials,
N = 242) to support the efficacy of inositol as monotherapy or adjunctive therapy in MDD.
93In contrast, a narrative review found that acetyl-L-carnitine was superior to placebo, and as effective as fluoxetine and amisulpride, as a monotherapy for mild to moderate depression.
94 It is generally well tolerated without significant side effects.
10,94The usual dose of
C. sativus (saffron) is 20 to 30 mg/day over 6 to 8 weeks.
95,96 One new meta-analysis (5 trials,
N = 177)
97 and 3 systematic reviews
96,98,99 further support its use as a monotherapy with comparable efficacy to antidepressants in mild to moderate MDD. Reported adverse effects of
C. sativus are mild and include anxiety/nervousness, increased appetite, nausea, and headache.
96Lavandula (lavender) doses are recommended at 2 to 4.5 mL/day (alcoholic tincture 1:2) or 6 to 12 mL/day (alcoholic tincture 1:5).
100 It has only been studied as an acute intervention in the short term (4-8 weeks).
69 In 1 RCT, the combination of
Lavandula and citalopram was significantly more effective than citalopram alone for moderate to severe depression.
101 Adverse effects of
Lavandula include nausea, confusion, and mild headaches.
69,101 Standard dose regimens for
R. rosea (roseroot) are not available in the literature, with studies reporting a range of 100 to 680 mg/day. It, too, has only been studied in the short term (4-8 weeks).
102 One RCT of
R. rosea monotherapy and sertraline in mild to moderate MDD found that neither condition was significantly different from placebo.
103 R. rosea has mild and infrequent side effects, including nervousness, dizziness, allergy, irritability, insomnia, fatigue, and unpleasant sensations.
102,103 Interactions with concomitant medications, such as theophylline and warfarin, have been reported.
104In summary, for mild to moderate MDD, acetyl-L-carnitine (Level 2 Evidence) is recommended as a third-line monotherapy and
C. sativus as third-line monotherapy or adjunctive treatment (Level 2 Evidence) (
Table 3). Folate (Level 2 Evidence) and
Lavandula (Level 3 Evidence) are recommended as third-line adjunctive treatments. Inositol and
R. rosea are not recommended for the treatment of MDD.