I Built a CBT Thought Analyzer API — No AI, No ML, Just Psychology

How I turned 11 cognitive distortion patterns from CBT therapy into a REST API with 3 endpoints — all running on a free Render instance. Now listed on RapidAPI.

What is CBT (Cognitive Behavioral Therapy)?

Cognitive Behavioral Therapy is the most evidence-based form of psychotherapy — decades of research show it works for anxiety, depression, OCD, and more. The core idea: your thoughts cause your feelings, not your circumstances.

A key CBT technique is identifying cognitive distortions — systematic errors in thinking that cause emotional distress. David Burns' Feeling Good identifies 11 common distortions:

1. All-or-Nothing Thinking — "If I'm not perfect, I'm a failure"
2. Overgeneralization — "One rejection means I'll always be rejected"
3. Mental Filter — dwelling on one negative detail
4. Discounting the Positive — "Those don't count"
5. Jumping to Conclusions (mind reading + fortune telling)
6. Magnification/Catastrophizing — "This will be a disaster"
7. Emotional Reasoning — "I feel guilty, so I must be guilty"
8. Should Statements — "I should be doing more"
9. Labeling — "I'm a loser" vs "I made a mistake"
10. Personalization & Blame — "It's all my fault"
11. Comparison — "Everyone is doing better than me"

The API

I built a REST API that detects these distortions in text input. No AI model needed — it uses evidence-based keyword-pattern matching for instant analysis.

Endpoints

Method	Path	Description
POST	/analyze	Detect CBT cognitive distortions (11 types)
POST	/procrastination	Detect procrastination patterns (8 types)
POST	/attachment	Detect attachment style (4 types)
GET	/health	Health check

Example: Analyze a Thought

curl -X POST https://cbt-thought-analyzer.onrender.com/analyze   -H "Content-Type: application/json"   -d '{"text": "I always mess everything up. Nothing ever goes right for me."}'

Response:

{
  "distortions": [
    {
      "name": "all_or_nothing_thinking",
      "confidence": 0.85,
      "evidence": "always mess everything",
      "reframe": "Is it really true that you ALWAYS mess up? Can you think of a time when things went well?"
    },
    {
      "name": "overgeneralization",
      "confidence": 0.80,
      "evidence": "always, nothing ever",
      "reframe": "Always and never are rarely accurate. What specific things have gone right?"
    }
  ],
  "summary": "2 distortions detected",
  "dominant_distortion": "all_or_nothing_thinking"
}

Why No AI Model?

Three reasons:

1. Cost — Pattern matching is free. LLM inference costs per-call.
2. Speed — Pattern matching returns in <100ms. LLM calls take 2-10s.
3. Determinism — The same input always returns the same output. No hallucination risk in mental health content.

The trade-off: pattern matching is less nuanced than an LLM. But for a first-pass screening tool that helps people identify their thinking patterns, the evidence-based keyword approach is fast, free, and reliable.

The Procrastination Detector

The /procrastination endpoint detects 8 procrastination patterns based on behavioral activation research:

• Perfectionism block
• Fear of failure
• Task overwhelm
• Waiting for motivation
• Task avoidance
• All-or-nothing approach
• Guilt-procrastination cycle
• Minimization trap

Each pattern comes with a CBT intervention — not just "you're procrastinating" but "here's the specific pattern and here's what research says helps."

The Attachment Style Detector

The /attachment endpoint uses Bartholomew's 4-type model (Secure, Preoccupied/Anxious, Fearful, Dismissing/Avoidant) based on two dimensions: avoidance of intimacy and anxiety about abandonment. Grounded in Miller's Intimate Relationships 8th edition.

Hosting on Render (Free Tier)

The API runs on a free Render web service. Free tier spins down after 15 min of inactivity, so the first request after idle takes ~10-15s (cold start). Subsequent requests are instant.

For production use, a $7/month Render instance eliminates cold starts.

Live on RapidAPI

The API is now listed on RapidAPI — giving built-in API key management, usage analytics, monetization (charge per-call), and discovery by 4M+ developers.

If you want to try the API directly, it's live at https://cbt-thought-analyzer.onrender.com. The GitHub repo with all 24 CBT tools is at github.com/alexcoledev/cbt-toolkit.

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This is not a replacement for therapy. It's a screening tool that helps identify thinking patterns. If you're struggling, please reach out to a licensed mental health professional.