There are a number of gentle and effective plants for anxiety that may help support your son through this transition:
Lemon Balm
(Melissa officinalis): A member of the mint family, this mild-tasting plant grows easily in the garden making it a great choice for families wanting to grow their own medicinal plants. An excellent herb for soothing the nerves, it promotes relaxation and sleep, and has an anti-spasmodic effect that can help calm troubled digestion.
Antique herbal texts praised Lemon Balm for the treatment of bad dreams. Its mild taste makes it a great choice for children and teenagers. A large handful fresh from the garden steeped in boiling water makes a pleasant herbal tea, with the addition of honey if required.
Chamomile
(Matricaria chamomilla) is another great sedative herb, suitable for all age groups. It is highly useful for treating mild anxiety, insomnia and digestive upsets, particularly when they are related to stress and tension.
Lavender
(Lavandula angustifolia): Lavender has been treasured for thousands of years for its delightful scent and its ability to balance emotions, uplift the spirits and relieve mild depression.
It is equally good for treating mild anxiety, nervousness and physical symptoms caused by stress, such as tension headaches, migraines and insomnia. Like Lemon Balm and Chamomile, it can help to settle digestive complaints exacerbated by anxiety and nervous tension.
Passionflower
(Passiflora incarnata): One of the best herbs known for supporting an overworked nervous system, Passionflower has relaxing and sedating properties making it an excellent herb for inducing restful sleep. Passionflower has no addictive effects, allowing the user to awake refreshed and alert in the morning - particularly important for teenagers heading back to school.
Your son could take a calming herb drink in a flask to school, or you may wish to brew him a cup when he comes home or is winding down in the evening. Taken during day time, these herbs are calming but they will not make him sleepy.
While I'm an advocate for combining and consuming these plants in the traditional manner of a medicinal tea, if your teenager hasn't grown up consuming herbal medicine then getting them to drink herbal tea might be easier said than done! But do give it a go, they taste delicious!
Luckily these plants are also commonly prepared in the form of an oral liquid that can be taken mixed with a little water or juice. If this is the case, seek out a reputable supplier of herbal medicines or your local Medical Herbalist who will be able to prepare you a suitable medicine from quality medicinal plants.
If his condition worsens or does not improve, see your leading healthcare professional.
References:
Muller, S. F., & Klement, S. (2006). A combination of valerian and lemon balm is effective in the treatment of restlessness and dyssomnia in children. Phytomedicine, 13(6), 383-387. doi: 10.1016/j.phymed.2006.01.013
Sarris, J., Panossian, A., Schweitzer, I., Stough, C., & Scholey, A. (2011). Herbal medicine for depression, anxiety and insomnia: a review of psychopharmacology and clinical evidence. European Neuropsychopharmacology, 21(12), 841-860. doi: 10.1016/j.euroneuro.2011.04.002