Friday, January 24, 2014

Tryptophan Depletion studies

The best review of tryptophan-depletion studies is by Moore et al. (2000).

 I think it is an accepted part of clinical psychiatric theory that serotonin obviously is related to mood, and the more serotonin there is, the better mood must be, and the less serotonin there is, the worse mood must be!  

With tryptophan-depletion, subjects are given a drink which results in a radical reduction in serotonin synthesis within hours.  It is strongly believed, though not rigorously proven, due to technical limitations, that such depletion results in a reduction of serotonin release by serotonergic neurons in the brain. 

The main consistent finding of these studies is that depressed patients who are treated with a serotonergic antidepressant, such as an SSRI, but who have not yet recovered fully from their depressive episode, are very sensitive to a sudden worsening in their depressive symptoms immediately after tryptophan-depletion. 

But, fully remitted patients tend not to have any depressive relapse following tryptophan depletion!

And depressed patients who have not yet received any antidepressant tend not to have worsening depressive symptoms following tryptophan depletion! 

And depressed patients treated with non-serotonergic antidepressants (such as desipramine) do not have worsened depressive symptoms following tryptophan depletion! 

There is little evidence that tryptophan depletion consistently affects panic or OCD symptoms. 

One study quoted in this review, by Delgado (1991), showed that in a group of untreated depressed patients given tryptophan-depletion, 37% actually improved following depletion, compared to 23% who got worse (by 10 points on the HDRS). 

It is obvious that momentary tryptophan depletion, and the resulting drop in serotonin synthesis, does not have consistent effects on psychiatric symptoms.  The effect is only reliable in partially treated patients taking SSRI's.  It may be that in these patients, it is a sudden induction of a withdrawal-like state which causes the sudden symptom change.  Or, it could be that in these patients in an early state of recovery, there is a temporary dependence on serotonin levels, which are working to "push"the patients towards recovery.  The tryptophan depletion suddenly removes the source of this "push", causing sudden relapse.  But serotonin clearly must not be the only possible way to "push"towards recovery, because depleting serotonin only has a negative effect on patients beginning SSRI treatment. 

Thursday, January 23, 2014

5-hydroxytryptophan (5-HTP)

The amino acid tryptophan is widely present in dietary proteins; it is metabolized, in a rate-limiting enzymatic step,  to 5-hydroxytryptophan in the brain, before being converted quickly into serotonin. 

5-hydroxytryptophan(5-htp) has been used as an antidepressant for many years, but little research apparently has been carried out recently, because it is not on a patent.

Cochrane reviews in 2001 and 2002 conclude that 5-htp probably is better than placebo for treating depression, but that the existing studies were of poor quality.

Here's a small randomized study comparing 5-htp with imipramine, with both groups showing similar improvements in depression symptoms. 
This 2004 study from the European Journal of Pediatrics shows that 5-htp given to children at a dose of 2 mg/kg at bedtime, led to a substantial reduction in night terrors over a 6-month period.  84% of the treatment group responded, compared to 29% of the placebo group.  The results were quite dramatic, with the average night terrors going down from 7 per month to 0.4 per month in the treated group, compared to a change from 7 to 3.4 in the placebo group.  There were no side effect problems.
This is an interesting opinion piece published in 2012.  However, there seem to be a lot of claims that are based on the authors' opinions, with references which look quite shaky and dated.  The main claim that I question is that 5-HTP causes a competitive inhibition of dopamine metabolism, thus leading in a longer-term basis to a hypodopaminergic state.  But another look at the basic science of this issue, such as described in this reference by Awazi (1978):, shows that serotonin itself relatively antagonizes dopamine function, but that exogenous 5-htp can actually cause a slight increase in dopaminergic activity, by displacing dopamine from storage sites and triggering a compensatory increase in dopamine synthesis. 

The bottom line about this dopamine issue should be to watch clinically for any signs of hypodopaminergic side effects (e.g. Parkinsonism) in any person using 5-htp supplements.  I actually don't see case reports along these lines. 

Wednesday, January 15, 2014

Zinc supplements in mental health

Zinc is a trace mineral which is necessary for a variety of metabolic functions in the body.  The neuropharmacology of zinc certainly includes NMDA-blockade effects, as well as a probable collection of other effects such as increasing BDNF expression. 

There is evidence that zinc supplements could be helpful to treat depression.  Here is a brief review of some pertinent studies:
In this very simple Polish study published in 2003, 14 patients with unipolar depression were randomized to receive either antidepressant + placebo, or antidepressant  + 25 mg zinc, for 12 weeks.  Both groups improved, but the zinc group had about 40% greater symptom reduction than the placebo group.  I appreciate the fact that in this paper, the complete set of data was shown, for each individual patient in the study.  This allows one to do a custom analysis of the data:  in this case, for example, there were several patients who appeared to be treatment-resistant in the placebo group,  and it was interesting to look at the results with these patients excluded, since they would otherwise skew the results in favor of the zinc group.  But even with this adjustment, the zinc group still had a significant, clinically relevant improvement compared to placebo.
This study done in 2009 looked at imipramine+ 25 mg/d zinc vs imipramine+placebo, for 12 weeks, in 60 unipolar depressed patients.  Here they found that for treatment resistant patients, the zinc group improved significantly more than the placebo group.  In effect, the zinc caused the treatment resistant group to respond as though it was no longer treatment resistant!   Yet, in this study, the zinc did not further improve symptoms in patients who were not treatment resistant.
Another simple 12-week study, done in Iran, of 25 mg/d added zinc or placebo, in 44 patients with major depression.  It was quite recent, from 2013.   The zinc group once again improved substantially more than the placebo group.   The study stands out in looking carefully at dietary intakes of various nutrients in all of the patients, to control for various dietary confounds.
another replication, from 2013
A 2013 meta-analysis, which concluded that zinc supplements have a clinically relevant effect in depression.
Another meta-analysis, from 2012.  Again it affirms the possible usefulness of zinc, not only for treatment of depression, but for prevention as well. 
This meta-analysis looked at zinc in treating ADHD, and the conclusions were largely negative.  There have been a few studies suggesting benefit, but these results seem not to be consistent enough to make a recommendation.  It is tempting to consider a trial of zinc augmentation as a deliberate trial for a an individual though, given the negligible risk.

Here is a link to my previous posting about zinc, which outlines some other uses in psychiatry, such as in eating disorders.  Also my other posting reviews some information about toxicity risks.
This interesting study showed that high dose zinc supplements (corresponding to about 60 mg/d in humans) given to rats actually led to a reduction in zinc levels in the hippocampus, and an impairment in memory performance.  The mechanism may be that higher serum zinc levels reduces synaptic release of zinc, through a negative feedback mechanism.  The article can be taken as a warning that more is not necessarily better!  The low-dose zinc supplemented group in this study did better, corresponding to a human dose of about 15 mg/d.

In conclusion, I think zinc supplementation is a reasonable, safe, evidence-based augmentation strategy for treating or preventing depression.  Most of the studies used 25 mg elemental zinc; I think this is a reasonable dose for an initial 12-week trial.  After this point, if continued zinc supplementation is to be used, I would suggest bringing the dose down to the 15-20 mg per day range, to rule out toxicity risks.  

Thursday, January 2, 2014

antidepressants in rapid cycling

In this short editorial by Michael Thase, the argument is made that  a diagnosis of bipolar II disorder is not necessarily a contraindication to antidepressant use for treating a depressive episode.

With these diagnostic categories, it is important to realize that there are relative risks of different management strategies, such as of antidepressants worsening rapid cycling.  But not all individuals necessarily will experience such an adverse effect.  We do not as yet have clear evidence ahead of time which can allow us to predict which patients with a particular diagnosis will experience benefit or adverse effect from a particular treatment. 

Part of the reason for this is that single diagnostic categories such as "bipolar II" or "rapid cycling" may represent a wide variety of ailments, which current diagnostic schemes cannot resolve, and may also represent numerous subsets of individuals, who may benefit or have adverse effects from different treatment strategies.

The best we can do, I think, is to use a type of Bayesian reasoning, in which current broad evidence should be our starting point to estimate risk or benefit.  In the case of rapid cycling, I think we must assume that there is a significant risk of adverse effects in rapid cycling bipolar patients.

But in an effort to treat a debilitating depressive state, there may be instances in which a riskier treatment could be warranted, as there is evidence that particular individuals can benefit.

Prazosin for PTSD update

In this article by Raskind et al. in the American Journal of Psychiatry (Sep. 2013), combat veterans with PTSD were given prazosin or placebo in a 15 week randomized study:

The prazosin was substantially beneficial for PTSD symptoms.  Dosing was on average about 5 mg in the mid-morning + 15 mg at bedtime.

There was a large, clinically relevant,  sustained difference from placebo, and the prazosin was well-tolerated.

The experience from this study differs from my own experience prescribing this drug, in that the doses were much higher.  Also, they used daytime doses, which I think shows acknowledgment that prazosin is not just useful for nightmares, but for all symptoms of PTSD, day and night.    I had previously prescribed in the 1-2 mg range, but I see there is a lot of room to move to higher doses, which could be much more effective without major safety or side-effect risks.