The effects of Acute Tryptophan Depletion in individuals with a history of depression with and without anger attacks

Symptoms of anger and aggression are very common in MDD patients, even though
these are not part of the psychiatric taxonomies (Van Praag, 1990). Van Praag
(2001) proposed a *subset of cases of depression* with anxiety and hostility as
primary symptoms, and in which low mood is a latecomer. These patients were
also thought to be more stress-vulnerable, have increased cortisol activity and
more pronounced serotonergic disturbances (Van Praag, 2001). Disturbances in
aggression regulation can be manifested inward (suicidal ideation,
self-mutilation) or outward (irritability, anger attacks) (Van Praag et al.,
1990). Fava (1998) characterized a subtype on a specific component of anger;
i.e. the presence of anger attacks (Fava,Rosenbaum, 1998; Fava,Rosenbaum,
1999), which are *sudden spells of anger accompanied by symptoms of autonomic
activation such as tachycardia, sweating, hot flashes, and tightness of the
chest which resembles panic attacks but without the predominant affects of fear
and anxiety* (Fava,Rosenbaum, 1998). Using the *Anger Attacks Questionnaire* (a
self-rating scale to assess the presence of anger-attacks (Fava, Rosenbaum,
McCarthy, Pava, Steingard,Bless, 1991), rates of anger attacks in MDD
outpatients have been reported around 40% (Fava, Nierenberg, Quitkin,
Zisook, Pearlstein, Stone,Rosenbaum, 1997).

While the clinical behavioural profile for MDD can be heterogenous, the most
consistent neurobiological finding is the association with impairments in the
serotonin (5-HT) system, as shown by various direct and indirect markers of
5-HT function (Maes & Meltzer 1994; Belmaker and Agam 2008). Decreased 5-HT
function is also still present in MDD patients in remission (Smith et al.,
1997; Neumeister et al., 2002). High risk relatives have been shown to be more
sensitive to 5-HT challenge procedures such as acute tryptophan depletion than
individuals without a psychiatric family history (Benkelfat et al., 1994; Van
der Veen et al. 2007), suggesting that impaired 5-HT function is not directly
related to a depressive state, but signifies a biological risk factor (*trait*)
for MDD.

There is some evidence that, within MDD samples, the largest 5-HT alterations
are in those MDD patients that have disturbances in aggression regulation, e.g.
suicidal patients and in MDD patients with anger attacks (Asberg et al., 1978;
Fava et al. 2000). In addition, we previously observed in a recovered sample of
MDD patients that the mood-lowering to Acute Tryptophan Depletion (ATD), an
experimental 5-HT challenge procedure known to transiently alter central
serotonin function, was largest in those former patients that had a history of
suicidal ideation during their previous episode (Booij et al., 2002). In a
sample of SSRI treated remitted depressed patients, depressed patients who had
serious suicidal thoughts or had attempts during a previous episode also had a
larger increase in anxiety, impulsivity, and reduced heart rate variability
(HRV) following ATD as compared to patients who never have had suicidal
ideation (Booij et al., 2006). Taken these findings together suggest that an
endophenotype of depression may exist, consisting of patients who have problems
with aggression regulation, and who have an increased reactivity to impaired
serotonin function. Whether this increased 5HT vulnerability persists beyond a
depressive episode and medication use, and thus represents a trait individual
MDD vulnerability factor for relapse is not known.

The aim of this project is to test the hypothesis that MDD patients with
disturbances in anger/aggression regulation have more serotonin disturbances,
as a trait marker for relapse, than MDD patients without disturbances in
anger/aggression regulation, using the ATD method. To this end, we compare
recovered MDD patients with and without a history of anger attacks during
their previous episode(s) lifetime. It is expected that recovered MDD patients
with a history of suicidal ideation have a greater serotonin vulnerability than
recovered MDD patients without a history of suicidal ideation, reflected in the
cognitive, physiological and behavioral response to ATD. Moreover, we expect
that anger expression during their episode or beyond (as measured by the
Spielberger trait anger scale) and suicidality during previous episodes will
predict response to ATD. Secondary aims are to explore the influence of
serotonergic genes (SERT; 5-Ht1A C(-1019)G) and MR / GR polymorphisms on ATD
response and investigation of differences in cognitive markers between these
groups. The project is part of a larger VENI project aimed to investigate the
neural, behavioural and cardiac mechanisms of anger and depression.

After a screening procedure to confirm final eligibility, two experimental
sessions will be carried out. This involves the ingestion of a tryptophan-free
(ATD) and a tryptophan-containing balanced mixture (placebo) under double
blind, counterbalanced conditions, with a minimum of 7 days apart. All sessions
including the screening procedure will take place at Leiden University Medical
center, at the dept of Psychiatry. A double-blind crossover design is used,
which means that participants as well as researchers and research-assistants
will be blind to the order in which the two sessions will be conducted.

The day before the session, all subjects will be instructed to fast from
midnight. The ATD mixture is similar to the one in Young et al. (1985), known
to decrease tryptophan levels by by 70 to 90% within about 6 hours after intake
(Young et al., 1985). It consists of the following amino acids: L-alanine 5.5
g, L-arginine 4.9 g, L-cysteine 2.7 g, glycine 3.2 g, L-histidine 3.2 g,
L-isoleucine 8 g, L-leucine 13.5 g, L-lysine monohydrochloride 11 g,
L-methionine 3 g, L-phenylalanine 5.7 g, L-proline 12.2 g, L-serine 6.9 g,
L-threonine 6.9 g, L-tyrosine 6.9 g, L-valine 8.9 g. The balanced (placebo)
mixture contains the same amino acids plus 2.3 g L-tryptophan (Young et al.,
1985). Because women weigh on average 16.7% less then men, the mixture will be
adjusted accordingly (Ellenbogen et al.1999). Because of the unpleasant taste
of L-methionine, L-cysteine, and L-arginine, these amino acids will be given in
capsules. The remaining amino acid mixtures are prepared just before oral
administration by mixing the powdered amino acids with about 200 ml water, 100
ml chocolate syrup, and 1.1 g of cyclamate (fake sugar). The amino acids will
be mixed with 200 ml orange juice for those who do not like chocolate.
Participants are asked to swallow the suspension in as short a time as possible
because of its somewhat unpalatable taste. After intake of the mixture,
participants spend the day in a private research room and are allowed to watch
neutral videos and to read neutral material. Sleeping is not allowed. About 3
hours after the protein mixture, subjects will be offered some low protein
snacks, incl. low protein cookies and/or low protein bread(@Loprofin), herb
bouillon and/or apple sauce.

To date, the ATD procedure has been carried out in more than 4200 subjects of
various diagnostic categories including depression, anxiety disorders, eating
disorders, schizophrenia and in healthy volunteers with and without a family
history of psychopathology. No major side effects have been reported. Both ATD
and the placebo procedure can produce transient nausea 1-2 hours after
ingestion of the mixture, and in a few cases vomiting. We previously conducted
four ATD studies in patients (three in remitted MDD patients, 1 in symptomatic
patients, about 70 patients total), and no serious side effects have been
observed. It is expected that ATD will lead to a transient mood-lowering in
about 60% of the patients (van der Does 2001; Booij et al., 2003; 2005a).
Previous studies in our own lab and in other labs showed that the mood-lowering
effect is transient (i.e. occur 5h after the ATD mixture, lasting for 3 hours
maximum), and a symptom exacerbation of similar magnitude as seen in
naturalistic relapse is rare (Booij et al., 2005).
There is no direct benefit from participating in the study. However, a more
systematic evaluation in remitted depressed patients that took part in a
similar experiment showed that the participants experienced increased insight
into their current and past functioning as a result of taking part in an ATD
study as an advantage (Booij et al., 2005).