Plants have a long history of use as spirit medicine. From extreme journeys of the soul, such as Ayuhuasca to commonplace rituals such as a soothing cup of chamomile tea.
With the recently increasing popularity of “botanical biohacking”, adaptogens, ancient tonic herbs, nootropics and anxiolytics long used by traditional medicine systems and natural health practitioners are making their way into the kitchens of increasing numbers of people, as their ability to significantly elevate the spirit becomes more widely known.
It should be noted that one of the reasons we have receptors for most of these mood-altering compounds is that our body has the capacity to produce them endogenously. Cannabinoids are one such example.
It should also be noted that when exposed to a substance in high doses or over a long period of time the neuro-receptors in the body may down regulate. So it is important to cycle certain herbs.
I believe that sometimes these plants can serve as simply a prompt to the body to re-cognize a state of bliss and balance.
All Adaptogenic herbs are also essentially mood regulators.. as by improving our ability to adapt to stress, we maintain healthy neuro-endocrine balance which ensures healthy mood regulation.
The biochemistry of emotion is complex and multifaceted... and I suspect we only understand the tip of the iceberg in regard to what makes us feel the way we do, and the effects of mood altering substances on our consciousness. That said, here are some of the most important compounds we know of that affect our mental, emotional (and spiritual) condition. And subsequently, some of the most effective plants for uplifting the soul.
Dopamine – responsible for desire and motivation, pleasure and reward. Low levels are linked to addictive behavior, depression, fatigue, mood swings, low sex drive, difficulty concentrating and forgetfulness. Too much can cause aggression, hyper-sexuality and schizophrenia.
5htp (5-hydroxytryptophan) – is the neurotransmitter responsible for feelings of happiness and wellbeing. Known for increasing focus, memory, pleasure, and overall mood improvement, it governs depression, mood, emotions, aggression, sleep, appetite, anxiety, memory, learning and perceptions, sexual desire and function, temperature regulation, and some social behaviour.
P.E.A. (phenylethylalamine) – “the love molecule”
Promotes feelings of attraction, excitement and nervousness and is associated with the initial euphoria of falling in love. This chemical acts as an anti-depressant by combining with dopamine that is naturally present in the brain.
Anandamide – “the bliss molecule”
Also produced endogenously, it binds to cannabinoid receptors. Anandamide is a messenger molecule that plays a role in pain, depression, appetite, memory, mood, and bestows a blissful feeling.
DMT (dimethyltryptamine) – “the spirit molecule”
Little is known about this substance except that it is found throughout nature, (not only in many plants, but also in trace amounts in the human body where its natural function is undetermined). It is a potent psychedelic when taken in high enough doses and many people attribute it to intensely spiritual experiences.
MAOIs (monamine oxidase inhibitors) – work by keeping monoamine feel good neurotransmitters (such as serotonin, dopamine, norepinephrine, DMT and P.E.A) circulating (preventing their removal by the enzyme monoamine oxidase) they make more of these brain chemicals available to effect changes in both cells and circuits that are impacted by depression.
When the initial phenylethylamine concentration in the brain is low, brain levels can be increased 1000-fold when taking a monoamine oxidase inhibitor (MAOI), particularly a MAO-B inhibitor, and by 3–4 times when the initial concentration is high. 
And the plants that affect them…
MUCUNA – one of the only naturally occurring (and certainly most concentrated) sources of L-dopa (the precursor to dompamine). Mucuna extract has been shown to increase not only dopamine concentrations, but also other neurotransmitters that affect mood, such as serotonin and norepinephrine too. It also contains DMT.
REISHI – Significantly elevates mood and sense of wellbeing by protecting dopaminergic neuron degeneration (demonstrated in clinical trials).
HE SHOU WU – Research has found that of all herbs, he shou wu is one of the greatest inhibitors of MAO activity. Which in turn allows for a greater amount of dopamine and other feel good neurotransmitters to be available in our system.
RHODIOLA - Induces feelings of relaxation and decreases anxiety by reducing the stress hormone cortisol significantly. It also stimulates the production of dopamine and serotonin as well as increasing the sensitivity of neurons to these neurotransmitters.
In animal studies, Rhodiola has also been shown to help repair damaged neurons in the hippocampus, a region of the brain considered to be the center for emotion, memory and the autonomic nervous system regulation. 
In a 2007 study published in the "Nordic Journal of Psychiatry", it was found to significantly reduce depression in patients with mild to moderate depression.
SCHISANDRA - has been found to reduce cortisol levels in the body (the stress hormone) and is effective in controlling changes in serotonin and adrenaline caused by stress. This adaptogenic berry also fights the adrenal fatigue that is linked to stress.
SHATAVARI - Shatavari stimulates and balances the production of happy hormones; endorphins, serotonin and dopamine - meaning it can greatly reduce mood swings, irritablility and menopause induced depression.
GOTU KOLA - Reduces anxiety, possibly through interacting with the relaxation-promoting neurotransmitter GABA, and has been demonstrated to increase levels of the neurotransmitters serotonin, norepinephrine, and dopamine in rat brains. It also lowers cortisol.
ROSE – Although there a few if any clinical studies on the effects of Rose on mood, it is used traditionally in Ayurveda to soothe hot emotions such as anger and soften the heart.
TULSI (found in our SHAKTI formula) - Tulsi has been shown to prevent stress-induced changes in blood levels of cortisol. It is a CNS stimulant (anti-stress agent) and has been used successfully in the treatment of Generalised Anxiety Disorder and has proven as effective as pharmaceutical antidepressant desipramine.
GINKGO (found in our RISHI blend) - The active compounds (including kaempferol) in Ginkgo are potent monoamine oxidase inhibitors and so regulate the amount of dopamine and other neurotransmitters in the brain. As we age MAO levels increase causing dopamine levels to fall. Research has shown that inhibition of this enzyme preserves brain function by protecting dopamine.
LIQUORICE (found in our OJAS blend) - is known to have 8 different anti-depressant compounds (all different MAOIs) Another compound, glycyrrhizin, breaks down cortisol, the stress hormone, enabling the body to deal with stress more efficiently.
PASSIONFLOWER (found in our soon to be released sleep and nerve blend) - the alkaloids chrysin and benzoflavone present in this herb have been found to increase GABA (gamma amino-butyric acid) in the brain. GABA is one of the inhibitory neurotransmitters, used by the brain to prevent over-excitement and attain balance. It also helps to decrease the activity of depression inducing brain cells.
As a final note… I believe part of the beauty of the human experience is the range and depth of emotions we are capable of experiencing, and usually there are lessons in them.. so called negative and positive emotions are 2 sides of the same coin and we often find that the presence of one carves out space for a deeper experience of the other. People who have felt deep grief and sorrow often find they ultimately have a greater capacity to experience joy and develop an inherent kindness that comes with a profound understanding of the condition of the human heart.
So we can view herbs as our allies, in balancing our biochemistry and tending to our energetic health, especially in the often stressful world we live in. However it can be dangerous to seek only the pleasant in life.. our emotions provide contrast and richness, and can be useful guides in showing us what needs to be attended to in our inner world. Outdated beliefs, unhealthy ways of relating or to show us where we’re not being true to ourselves. And sometimes acceptance and non-judgemental witnessing is all that is required to dissipate the pain of intense, seemingly negative emotions.
We use these plants to fortify our bodies.. both physically and energetically. To soothe anxiety or lift the fog of depression, to provide assistance in regulating physiological functions or remind our body what a flood of serotonin or dopamine feels like, when it seems to have forgotten. And hopefully, we trigger an internal mechanism whereby balance is more easily found, and we discover (or rediscover) just how good we are designed to feel.