Cannabis Classification by Chemotype (Type I-V): The Modern Chemical System

ChillTokin · July 24, 2026, 7:03am

Cannabis Classification by Chemotype (Type I-V)

Chemical Classification — Modern Science Replacing Indica/Sativa

Asiannabis Community - General Discussion
Updated: July 2026

1. Why Classify by Chemotype?

The Indica/Sativa/Ruderalis system was created in the 18th century (Lamarck, 1785) based on morphology — height, leaf shape, flower density. However, after over 100 years of crossbreeding, the morphological boundaries between “subspecies” have virtually disappeared.

A large-scale genomic study by Watts et al. (2024) on 8,000+ commercial cannabis samples showed that: “Indica” or “Sativa” labels cannot predict the actual cannabinoid or terpene composition of a plant. In other words, you cannot tell how much THC or CBD a strain contains just by looking at its leaves.

Chemotype — classification based on chemical composition — solves this problem. The system proposed by Small & Beckstead (1973) and expanded by Mandolino & Ferrante (2024) divides cannabis into 5 clear groups, measurable by HPLC or GC-MS.

2. The Five Main Chemotypes

Chemotype	THC:CBD Ratio	Primary Cannabinoid	Applications
Type I	High THC >5:1	THC 15-35%	Medical (pain, insomnia, PTSD)
Type II	Balanced 1:1-5:1	THC+CBD similar	Medical (reduced psychoactive side effects)
Type III	High CBD <1:5	CBD 10-20%, THC<1%	Wellness, legal hemp
Type IV	High CBG	CBG 10-20%	Research, anti-inflammatory
Type V	No cannabinoids	<0.1%	Fiber, food, construction

3. THCAS vs CBDAS Gene — The Chemotype Determinant

Chemotype is primarily determined by a single gene locus on the chromosome encoding synthase enzymes:

THCAS (THCA synthase) — converts CBG-A → THC-A
CBDAS (CBDA synthase) — converts CBG-A → CBD-A

Genotype	Chemotype	Result
BT/BT	Type I	High THC, virtually no CBD
BT/BD	Type II	Both THC and CBD
BD/BD	Type III	High CBD, virtually no THC

Key point: Broad or narrow leaf shape is NOT related to THCAS/CBDAS genes. Only genetic testing or chemical analysis can accurately determine chemotype.

4. Over 150 Cannabinoids — Beyond THC and CBD

As of 2025, scientists have identified over 150 phytocannabinoids in cannabis:

Cannabinoid	Origin	Research Potential
CBN	THC degradation	Sleep aid
CBC	From CBCA synthase	Anti-inflammatory, antidepressant
THCV	African strains	Appetite suppression, anti-diabetic
CBDV	Hemp varieties	Epilepsy, autism
CBG	Precursor to all cannabinoids	Antibacterial, anticancer
Delta8-THC	THC isomer	~50% less potent

5. Terpene Profile & Entourage Effect

Cannabis produces over 200 terpenes. Russo (2011, 2019) proved that terpenes interact synergistically with cannabinoids — called the “entourage effect”

Terpene	Aroma	Biological Effect	Entourage
Myrcene	Mango, herbal	Sedative, muscle relaxant	Enhances THC absorption through BBB
Limonene	Citrus	Anxiolytic, mood elevator	THC+Limonene reduces anxiety
Beta-Caryophyllene	Black pepper	Anti-inflammatory	Binds CB2 receptor directly
Linalool	Lavender	Sedative, anticonvulsant	Enhances CBD seizure reduction
Alpha-Pinene	Pine	Bronchodilator, focus	Counteracts THC memory impairment
Terpinolene	Floral, pine	Mildly sedative	Found in “Sativa” varieties
Humulene	Hops	Appetite suppressant	Anti-inflammatory with CBC
Ocimene	Basil	Antifungal, antiviral	Needs more research

Practical implication: Two Type I strains (both THC 25%) with different terpene profiles will produce entirely different effects.

6. Autoflower Has Reached Photoperiod Quality

Modern breeding programs (2020-2026) crossed Ruderalis genes into elite photoperiod genetics through 5-8 generations of backcross:

THC autoflower now reaches 25-30% (equivalent to photoperiod)
CBD autoflower: Type III achieving 15-20% CBD, THC < 0.3%
Life cycle 70-90 days → 4 harvests/year outdoors
No photoperiod dependency → year-round cultivation in tropics

7. Strain Selection Guide by Chemotype

Instead of asking “Indica or Sativa?” start with: “What chemotype do I need?”

5-Step Selection Process:

Identify the chemotype needed (Type I-V) based on purpose
Select appropriate terpene profile to fine-tune effects
Verify COA from third-party laboratory
Beginners → start with Type II or Type III
Keep a usage journal to find your optimal formula

References

Small & Beckstead (1973). Nature, 245, 147-148.
Russo (2011). British J Pharmacology, 163(7), 1344-1364.
Russo (2019). Frontiers in Plant Science, 9, 1969.
Laverty et al. (2019). Genome Research, 29, 146-156.
Grassa et al. (2021). New Phytologist, 230(4), 1532-1543.
Watts et al. (2024). Nature Plants, 10, 1234-1244.
Mandolino & Ferrante (2024). Phytochemistry Reviews, 23(2), 401-420.
ElSohly et al. (2017/2025). Progress Chem Org Nat Prod, 103, 1-36.
Morales et al. (2017). Progress Chem Org Nat Prod, 103, 159-220.
de Meijer et al. (2003). Genetics, 163(1), 335-346.
Vergara et al. (2021). PeerJ, 9, e10672.
Tahir et al. (2021). J Cannabis Research, 3, 7.
Viet Growers Community (2015). Viet Grower Handbook.

Legal Disclaimer: This article is for educational purposes only. In Thailand, cannabis is regulated under the Controlled Herbs Act 2025 and Ministerial Regulation B.E. 2569. All activities must comply with PT33 licensing. Recreational use is prohibited.

Asiannabis Community — asiannabisthailand@gmail.com